~T~ 630 Certificate

RESPONSE OF BENTHIC COMMUNITY STRUCTURE TO HABITAT HETEROGENEITY IN INDIAN OCEAN

A Thesis submitted to Goa University for the Award of the Degree of

DOCTOR OF PHILOSOPHY in Marine Science

Sabyasachi Sautya (M.F.Sc) CSIR - National Institute of Oceanography Dona Paula, Goa !

Research Guide

Dr. B.S. Ingole Chief Scientist Biological Oceanography Division CSIR - National Institute of Oceanography Dona Paula, Goa, INDIA

Goa University, Taleigao Goa 2013

T - 6 3 0 ~T~ 630 CERTIFICATE

This is to certify that Mr. Sabyasachi Sautya has duly completed the thesis entitled “Response of benthic community structure to habitat heterogeneity in Indian Ocean” under my supervision for the award of the degree of Doctor of Philosophy. This thesis being submitted to the Goa University, Taleigao Plateau, Goa for the award of the degree of Doctor of Philosophy in Marine Sciences is based on original studies carried out by him. The thesis or any part thereof has not been previously submitted for any other degree or diploma in any University or Institutions.

Date: 2 & U 1 2 0 1 3 CSIR-National Institute of Place: Dona Paula Oceanography Dona Paula, Goa-403 004

c&r \ J n .I) ^ DECLARATION

As required under the University Ordinance 0.19.8 (iv), I hereby declare that the present thesis entitled “Response of benthic community structure to habitat heterogeneity in Indian Ocean” is my original work carried out at the National Institute of Oceanography, Dona-Paula, Goa and the same has not been submitted in part or in full elsewhere for any other degree or diploma. To the best of my knowledge, the present research is the first comprehensive work of its kind from the area mentioned. The literature related to the problems analyzed and investigated has been appropriately cited. Due acknowledgements has been made wherever facilities and suggestions has been availed of.

Sabyasachi Sautya This Thesis is VecRcatecC to M y Parents JAncC M y PeCovecC'Wtfe ACKNOWLEDGEMENT

First of all, I am grateful to The Almighty GOD for establishing me to fulfill this work.

Foremost, I express my deep sense of gratitude and sincere thanks to my research guide Dr. B.S. Ingole, Scientist, National Institute of Oceanography, Goa, for the continuous support of my PhD study and research, for his patience, motivation, enthusiasm, and immense knowledge. His guidance helped me throughout my research and writing of this thesis. I got all the freedom during my work which helped me to think differently and broadly, sometime scientific way, sometime realistic or sometime philosophical way, this because of you sir. Thank you so much sir.

I wish to sincerely thank Dr. S.R. Shetye, Director (former), National Institute of Oceanography, Goa for providing me all the facilities during my PhD work and an excellent research environment.

I would like to thank my FRC committee members: Prof. G.N. Nayak, Head of the Dept, of Marine Science, Goa University for his kind consideration to be my co-guide and Dr. C. Mohandass, Scientist, NIO, Goa my VC’s nominee, for his valuable comments, support and encouragement.

I would like to thank the administrative staff of Goa University and National Institute of Oceanography, Goa for all their help during my PhD work.

I wish to express my sincere gratitude to the CSIR for financial support to the Net-Work project ‘Indian Ridge studies’ which supported me to onboard sampling during my project assistant period (March, 2006 - Dec, 2008). I gratefully acknowledge the funding sources that made my thesis work possible. I thank the CSIR for providing financial assistance as the Senior Research Fellowship Award (Dec, 2008 - Dec, 2011) which enabled me to complete my thesis research work.

1 express my sincere gratitude to Dr. K.A. KameshRaju, Dr. R. Sharma, Dr. R. Nigam, Dr. B.N. Nath and Dr. A.B. Valsangkar for selecting me as a participant during various cruises under their Project leadership. My heartiest thanks to Durbar Ray for helping me to collect biological samples from RV Sonne and Akademic Boris Petrov cruise, and valuable inputs during my thesis writing. I gratefully acknowledge Dr. C. Prakashbabu for allowing me to handle the CNS and CO2 Culometer analyzer, Dr. M. Kocherla for the Particle Size analyzer and Mr. V. D. Khedekar for his help during Scanning Electron Microscopy, K. Samudrala for helping CR and Seamount maps preparation, at NIO, Goa, India.

I express my sincere gratitude to the scientific team, the Captain and crew members of ‘ORV Sagar Konya' and ‘Akademic Boris Petrov’ for their help during sampling in western Indian continental margin and Central Indian Ocean Basin. I am thankful to the captain of the cruise ‘RV Sonne' and his group for help in collecting the underwater video images and the priceless samples from the Carlsberg Ridge and Andaman Back-arc Basin.

1 gratefully acknowledge CenSeam (A Global Census of Marine Life on Seamounts - a CoML project) for travel support under the "CenSeam minigrant programme 2010" to analyze the sponge and associated fauna at P.P. Shirshov Institute of Oceanology of Russian Academy of Sciences, Moscow and seamount brittle star samples at Natural History Museum, Stockholm, Sweden. 1 am grateful to Dr. K. R. Tabachnick for guiding me on identification of deep-sea Hexactinellid sponge during my stay at P.P. Shirshov Institute of Oceanology, Moscow. I am also thankful to Dr. S. Stohr who taught me the identification methods on deep-sea brittle stars during my stay at Natural History Museum, Stockholm, Sweden. I gratefully acknowledge “InterRidge/ISA Endowment Fund Postdoctoral Fellowship 2011” for the opportunity to carry out video data analysis at the National Oceanography Centre, Southampton, UK. My special thanks to Dr. Daniel Jones for guiding me to analyze the underwater video during my stay at NOC, UK.

My sincere acknowledgement to the DST for travel support to attend the International workshop on “MeshAtlantic - Video Survey Techniques Workshop” CCMAR, University of Algarve, Faro, Portugal.

I wish to thank to Mr. Alexey Rajsky, Dr. O. E. Zezina from P.P. Shirshov Institute of Oceanology of Russian Academy of Sciences, Moscow for identify the deep-sea Pycnogoida and Brachipoda. I am grateful to Prof. Paul Tyler, Dr. David Billett, and Dr. Andrew Gates for their important inputs during benthic faunal identification and data analysis at NOC, UK. 1 also thank Dr. Jaygopal Pattanayak (Zoological Survey of India, Kolkata, India) for helping me to identify the demospongiae.

I would like to acknowledge Dr. M. P. Tapaswi, Librarian, and his staff for their efficient support in obtaining the literature and maintaining good journals.

I am indebted to all my ‘Benthos’ labmates Dr. Mandar Nanajkar, Dr. Sandhya, Dr. Sini Pavithran, Reshma, Uday, Abhay, Indranil and Darwin who have contributed immensely to my personal and professional life and for all the help and support they have rendered to me whenever I needed. Without mention the name Dr. Sanitha Sivadas this thesis would be incomplete, she helped me a lot to understand all the subjects specially in statistics and taken care like her brother during my thesis, so many thanks to you Sanithadi. Without mentioning my friends group this journey will be incomplete. The people of this group Rubail, Vikrant, Dr. Arif, Swaraj, Girish, Sumanta, Anil, Amit, Sandeep, Navnath, Shrikant and Hrishikesh for their moral support and motivation, which helped me to give my best and made my stay at NIO, Goa a wonderful experience. My dear friends thank you all for filling up my canvas of memories with several shades which will remain with me forever.

My heartfelt thanks to all of my music club (Dr. Anindya Mazumdar, Amol, Amab, Priyabrata, Rakesh, Swatantra, Partirupa, Shisir, Puja, Gobardhan, Neelava, Nishant and Devdutt) and NIO cricket club (Madan sir, R. Madhan, Kishan, Asok, Saba, Kartik, Suresh, Dinesh, Santodh, Suharsh, Mutthukumar, Harish and Shyam) members who also made this journey memorable to me. 1 would like to thank to my seniors Dr. R. Saraswat, Dr. Ravi, Dr. Anand, Dr. S. Damare, Dr. S. Rana, Dr. R. Roy, Dr. P. Das, Dr. Mahesh and Dr. P. Chakraborty for their various support during my work.

I would like to thank my parents Shri Bivash Sautya and Smt. Manisha Sautya, and grandpa Shri Satish Chandara Sautya and other all family members for their love, support and encouragement throughout my life. I specially thank to my wife’s nephew ‘MikaP who supports me mentally with his voice and smile. I also wish to thank to my in-laws especially my mother- in-law Smt. Shibani Das and Uncle Ashis Manna for their all support.

Last but not the least; I thank to my wife ‘Babai’ for her love, care, patience, continuous support and encouragement from ‘Jab (when) We Met’.

Thank you all... Contents

Chapter-1 General Introduction Page No. 1.1 Introduction 1 1.2 Ocean habitats 2 Geomorphological features of the sea 3 floor Continental margins 4 Abyssal floor 5 Mid-oceanic ridges 5

1.3 Benthic communities and their classification 5 Importance o f benthos 6 1.4 Role of habitat heterogeneity instructuring and maintaining the benthic 7 diversity Continental margins 7 Deep-sea 8 1.5 Benthic research in Indian Ocean 10 Geography 10 History 11 Benthic biodiversity 12 1.6 Objectives of the study 14

Chapter-2 Macrofaunal community structure of the western Indian continental margin including Oxygen Minimum Zone

2.1 Introduction 15 Objectives 18 2.2 Oceanographic settings of the study region 19 Study area 20 2.3 Materials and Methods 20 Laboratory analysis and data processing 21

2.4 Results 22 Environmental settings 22 Macrofaunal population structure 23 Biomass size spectra 24 Composition 25 Dominant taxa 26 Multivariate analysis o f community 27 structure Diversity indices 28 Distribution o f polychaete feeding types 28 Correlation of environmental and 28 community parameters 2.5 Discussion 29 Macrofaunal population structure: 29 density, composition and biomass Influence of habitat heterogeneity on 32 macrofaunal community structure

Chapter - 3 Community structure and small-scale spatial pattern of deep-■sea macrofauna in Central Indian Ocean Basin (CIOB)

3.1 Introduction 71 Objectives 17 3.2 Materials and Methods Statistical analyses 7 : 3.3 Results 74 Environmental parameters 74 Macrofaunal abundance: Population 74 density, biomass and composition Spatial pattern 75 Cluster analysis 76 Species Diversity 76 Feeding types 76 Correlation of biotic and abiotic 76 parameters 3.4 Discussion 77

Chapter - 4 Megafaunal community structure in Andaman Back-arc Basin including seamounts 4.1 Introduction 86 Objective 88 Hypothesis 88 4.2 Study area 89 4.3 Materials and Methods 89 Data collection 90 Image analysis 91 Statistical analysis 92 4.4 Results 94 Habitat structure 94 Megafaunal community structure 95 Assemblage composition and dominant 95 taxa Multivariate (MDS) analysis o f 97 substratum types and megafaunal community Diversity indices 98 Correlation between substratum types 98 and biotic community parameters 4.5 Discussion 99 4.6 New insights from the present study 102 4.7 Conservation of Andaman seamounts 102

Chapter-5 Megafaunal community structure in mid-oceanic ridge: habitat- scale pattern on the Carlsberg Ridge

5.1 Introduction 119 Objectives 121 5.2 Geophysical settings of the study area 122 5.3 Materials and Methods 122 Image processing and Data analysis 123 Statistical analysis 124 5.4 Results Habitat structure 125 Megafaunal assemblage composition 126 Megafaunal density and diversity: 127 constraints on habitats Multivariate analysis: Groupings of 128 habitat based on nature of substratum, water depth andfaunal community Relationship between type of habitat and 129 megafaunal community 5.5 Discussion 130 5.6 Biological potential of Carlsberg Ridge 132

Chapter-6 Discovery of species 6.1 Introduction 148 6.2 Necessity of species description 148 6.3 How new species are described? 149 6.A Description of a new species of Hyalascus (Hexactinellida: Rossellidae) 151 from a volcanic seamount in the Andaman Sea 6.B A new genus and species of deep-sea glass sponge (Porifera: 156 Hexactinellida: Aulocalycidae) from the Indian Ocean 6.C Brittle stars (Echinodermata: Ophiuroidea) from seamounts in the 164 Andaman Sea (Indian Ocean) - a first account, with descriptions of new species

Chapter - 7 Summary and Conclusion 192

Bibliography 196 LIST OF TABLES

Table 2.1a. Environmental characteristics observed on the western Indian continental margin.

Table 2.1b. Environmental characteristics of habitats examined at the 14°N latitude

Table 2. 2. Taxon list and density (ind.m'2) data for Western Indian Continental Margin macrofauna.

Table 2.3. Rank wise dominant taxon along the study area.

Table 2.4 Macrofaunal diversity along the western Indian continental margin

Table 2.6. Correlation between biotic and abiotic parameters in the study area

Table.3.1. Details of sampling locations and environmental parameters along the study

Table 3.2. Macrofaunal taxonomic details along the study area

Table 4.1. Video observations on seamounts (CSM and SM2) and bathyal sea floor (back-arc basin) in the Andaman Sea. Detail of locations, depths and approximate area covered for each transect conducted by the TVG (television operated video gripper).

Table 4.2. Composition of substratum types used for assigning substrate codes to observed habitats viewed from video images from the TVG in the Andaman Back-arc Basin.

Table 4.3. SIMPER analysis of the substrate on two seamounts (CSM and SM2) in the Andman Back-arc Basin; average abundances (av. abund), average Simper (av. simp), contributed percentage (contrib%) and cumulative contribution (cum%).

Table 4.4. Abundance SIMPER analysis of faunal communities on two seamounts (CSM and SM2) in the Andman Back-arc Basin; average abundance (avg. abund), average similarity (as. simp), contributed percentage (contr%), cumulative contribution (cum%). Table 4.5. SIMPER analysis of average abundance dissimilarity between organism groups A and B on two Andaman Sea seamounts. Average dissimilarity = 91.92. Average abundance (av. abund), average dissimilarity (av. diss), quotient of dissimilarity and standard deviation (diss/SD), contributed percentage (contrib%), cumulative contribution (cum%). Here we presented the faunal contribution percentage for dissimilarity between the groups up to 50%.

Table 4.6. RELATE analysis between substratum types and biotic parameters in the Andaman Back-arc-Basin (ABB). Bold numbers indicate significant values.

Table 4.7. Linear regression based on Pearson correlation showing the relationship between the substratum types and faunal diversity parameters in the Andaman Back-arc Basin. Bold numbers indicate significant values.

Table 5.1. Details of underwater video observation and their geographical locations along the Carlsberg Ridge, Indian

Table 5.4. Correlation between habitat types and megafaunal groups, biotic indices (values in bold and italics are significant).

Table 6.1. Spicule dimensions of Indiella gen. n. ridgenensis sp.n. (in mm). L - length, D - diameter, d - diameter of a primary rosette (N = number of observations; Min = minimum; Max = maximum; Avg = average; SD = standard diviations). Bold measurements are used in the text sections. LIST OF FIGURES

Figure 2.1. Map showing stations location in the study area with respect to bathymetric gradients and legends indicating the sample collected depth range; 3D map also showing the stations locations with better view about the study area.

Figure 2.2. Dissolved oxygen concentration values measured by DO sensor attached with CTD along the water depths at 11 °N and 12°N latitude of western Indian continental margin.

Figure 2.3. Depth as well as region-wise macrofaunal density and their distribution map along the study area

Figure 2.4. Depth-wise macrofaunal biomass and distributional map along the study area

Figure 2.5. Occurrence percentage of mean biomass size-spectra for the marobenthic assemblages in the study area

Figure 2.6 Macrofaunal composition at different geophysical provinces of the study area

Figure 2.7. Cluster and nMDS based on of average macrofaunal density along the study area.

Figure 2.8. Distribution of macrofaunal diversity ([a] Margalefs index d and [b] Shannon-Wiener index H ’) along the western Indian continental margin.

Figure 2.9. Distribution of Polychaete macrofaunal feeding types along the western continental margin (shelf, slope and basin waters).

Figure 2.10. Photograph of anterior part of Paraprionospiopinnata with well- developed branchia observed in upper the slope OMZ

Figure 3.1. Bathymetric map of the sampling locations at Central Indian Ocean Basin Figure 3.2. Distribution of macrofaunal density throughout the study area. Figure 3.3. Station wise macrofaunal biomass along the CIOB. Figure 3.4. Macrofaunal group composition along the CIOB area. Figure 3.5. Box core wise macrofaunal composition in CIOB. Figure 3.6. Cluster analysis of macrofaunal abundances in the CIOB. Figure 3.7. Station wise faunal diversity distribution along the CIOB.

Figure 4.1. Bathymetric map of the Andaman Back-arc Basin including Andaman Back-arc Spreading Centre (ABSC) and locations of the underwater video transects (TVG).

Figure 4.2. Composition of substratum types of two seamounts and surrounding sea floor in the Andaman Back-arc basin, with transect codes.

Figure 4.3. Megafaunal abundance along depth for two seamounts and the surrounding deep sea in the Andaman Back-arc basin.

Figure 4.4. Megafaunal group composition along the CSM and SM2 seamounts and basin area in the Andaman Sea Back-arc Basin.

Figure 4.5. Structure of the CSM seamount with accurate locations of the TVG-10 at summit and TVG-9 at flank, and the fauna associated with it. Megabenthic communities observed on a crater seamount in the Andaman Sea.

Figure 4.6. The SM2 seamount with locations of TVG-12 at summit and TVG-11 at flank, and its associated fauna.

Figure 4.7. Occurrences of motility catagories on both seamounts and the basin area.

Figure 4.8. nMDS analysis of substratum types along the study sites in the Andaman Sea, the seamounts CSM and SM2, and the off axis basin.

Figure 4.9. nMDS analysis of megafaunal community along the study sites in the Andaman Sea, the seamounts CSM and SM2, and the off axis basin.

Figure 4.10. Transect-wise distribution of megafaunal community structure indices

Figure 4.11. Number of taxa reported from the Indian Ocean seamounts including the present study..

Figure 4.12. Comparison of sponges recorded from seamounts around the globe.

Figure 4.13. Map of Pheronema sp. distribution on the world ocean seamounts. The white circle indicates the new addition of Pheronema sp. from the seamounts in the Indian Ocean.

Figure 5.1. Transect locations of the study area: Shallower transects TVG 2 & 3 and deeper transects TVG 1 & OFOS 1 located in the northern segments; other all deeper transects TVG 4, 5, 6, 7, 8 and OFOS 2 & 3 located in the southern segments in the Carlsberg Ridge.

Figure 5.2. Habitat guides o the study area Figure 5.3. Habitats distribution, composition, dominant habitat and species associated to suitable habitat types along the transects.

Figure 5.4. Megafaunal group composition along the study area

Figure 5.5. Faunal density along the transects

Figure 5.6. Megafaunal diversity along the transects.

Figure 5.7. nMDS of habitat types along the CR

Figure 5.8. Cluster analysis of megafaunal communities along the study area

Figure 5.9. Relationship between water depths and faunal abundances in the study area.

Figure 5.10. Relationship between faunal total count and area occupancy.

Figure 6.A.I. Hyalascus andamanensis sp. nov.

Figure 6.A.2. Hyalascus andamanensis sp.nov., spicules of the holotype.

Figure 6.A.3. Map showing the distribution of Hyalascus in the world Oceans.

Figure 6.B.I. Global distribution of Aulocalycidae including the present study. Figure 6.B.2. Indiella gen.nov. ridgenensis sp.nov. Figure 6.B.3. Indiella gen.nov. ridgenensis sp.nov. drawings of spicules of the holotypes.

Figure 6.B.4. Scaning Electron Microscopy of Indeilla gen.n. ridgenensis sp.nov. Frameowrk and spicules of the holotypes..

Figure 6.C.I. Ophioleuce longispinum sp. nov., holotype, SEM images.

Figure 6.C.2. Ophioleuce longispinum sp. nov., arm skeleton, SEM images.

Figure 6.C.3. Ophiophyllum minimum sp. nov., holotype, SEM images.

Figure 6.C.4. Ophiophyllum minimum sp. nov. arm skeleton, SEM images.

Figure 6.C.5. Astrophiura cf. tiki. A, dorsal aspect; B, ventral aspect. Ophiura sp., C, dorsal aspect; D, ventral aspect. Labelling for Astrophiura follows the tradition for this genus, c, centrodorsal plate; b, basal plate; d, dorsal arm plate; ir, interradial plate; r, radial plate; v, ventral arm plate. Remaining abbreviations as in Figure 2. Scale bars in millimetre, remaining abbreviations as in Figure 6.C.I. Figure 6.C.6. Ophiactis perplexa: (A) dorsal aspect; (B) ventral aspect; (C) arm dorsally. Ophiolimna antarctica: (D) dorsal aspect; (E) ventral aspect. Scale bars in millimetres. LIST OF PLATES Plate 2.1. Sample analysis during the study in western Indian continental margin.

Plate 2.2. Some dominant macrofauna along the western Indian continental margin.

Plate 3.1. Techniques used to collect sample in CIOB

Plate 3.2. Arthropods from Central Indian Ocean Basin.

Plate 5.1. Techniques used for sampling in Andaman Back-arc Basin and Carlsberg Ridge, Indian Ocean.

APPENDIX

Appendix 1. Taxonomic list of megafaunal communities from Andaman Back-arc Basin including seamounts.

Appendix 2. Megafaunal taxon list (presence and absence data) observed during underwater video survey in Carlsberg Ridge. Abbreviations

ABB - Andaman Back-arc Basin BSS - Biomass size spectra BSX - Sessile, sub-surface deposit feeder and other structure CIOB - Central Indian Ocean Basin CMJ - Carnivore, motile and jawed CoML - Census of Marine Life Corg - Organic carbon CR - Carlsberg Ridge CSM - Cratered seamount CTD - Conductivity Temperature Depth dd - disk diameter DO - Dissolved oxygen FDP - Filter-feeding, discretely motile, pumping GBIF - Global Biodiversity Information Facility IIOE - International Indian Ocean Expedition MNHN - Museum national d'Histoire naturelle, Paris MOR - Mid-oceanic ridge NE - North-east nMDS - Non-metric multi dimensional scaling OFOS - Ocean Floor Observation System OM - Organic matter OMZ - Oxygen minimum zone POM - Particulate organic matter RVS - Research vessel Sonne SD - Standard deviation SDT - Surface deposit feeder, discretely motile and tentaculate SEM - Scanning Electron Microscopy SIMPER - Similarity percentage SK - Sagar Kanya SMNH - Swedish Museum of Natural History SMT - Surface deposit feeder, motile and tentaculate SMX - Surface deposit feeder, motile and other structure SW - South-west TVG - Television Gripper UNAM - Coleccion Nacional de Equinodermos Mexicanos Chapter 1 General Introduction Introduction Chapter - 1

Over 60% o f our_pCa.net is covered by water more than a miCe deep, dhe deep sea is the Congest habitat on earth and is CargeCy unexpCored More peopCe have traveCCed into space than have traveCCed to the deep ocean reaCm.... The BCue TCanet Seas of Life

1.1 Introduction

W e believe that the most beautiful things in the universe is “Life and its diversity” which begin over 4.2 billion years ago, while the earth formed 4.56 billion years ago. The first land masses came to existence over 3 billion years ago which is 1.2 billion years younger than the life, making the Ocean the source of origin of life. The variety of life, i.e multi cellular organism came after 1 billion years ago of landmass formation which is also collectively called Precambrian1 period in geological history. At present there are millions of varieties of organisms in this unique planet ‘Earth’. Now the question comes - Why the living organism present only in the Earth, not in any other planet? The simple answer is other planets are having different environment which does not support the existence of life. Another question arises that- Why there is so much diversity of life in this planet? The answer is again simple i.e the environmental heterogeneity throughout the aquatic and terrestrial biomes. Compared to the terrestrial ecosystem, aquatic ecosystem supports more than 50% of all the species on Earth (http://oceanservice.noaa.gov). The aquatic environments are represented by pond, estuary, river and ocean while terrestrial is characterized by mountains, plains, rain forest, and

1 The Precambrian is geological time scale which describes the large span (4570 - 541 Ma) of Earth history before the current Phenerozoic.

'Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean

1 1 P a iz e Introduction Chapter - 1

grassland. Natural ecosystems are open systems composed of interconnected gradients, patches and networks, in which matter, energy, information and organisms are continuously exchanged (Dodds and Rothman 1999; Levinton and Kelaher 2004; Fukami and Wardle 2005; Godbold and Solan 2009).

1.2 Ocean habitats

The area of Earth is about 510 million square kilometers. Of this total, approximately 360 million square kilometers, or 71 percent, is represented by oceans and smaller seas such as the Mediterranean Sea and the Caribbean Sea. Continents and islands comprise the remaining 29 percent, or 150 million square kilometers. The world ocean can be divided into four main ocean basins—the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, and the Arctic Ocean. Oceans cover 71% of the Earth surface and strongly modify the climate. There are many habitats in this biggest ecosystem. Habitat is a type of environment which is preferred by some specific or group of organisms. Habitats in the ocean can be divided into distinct realms where changes in terrain and oceanographic patterns create ecological niches for life. Oceans are characterized by various types of habitats which is influenced by topographical features, geological (e.g., sediments or bottom substrata) and physico-chemical (e.g., temperature, salinity, dissolved oxygen etc.) properties. The most important features of the Ocean floor are the continental margin, mid-oceanic ridges, trenches, submarine canyons, seamounts, abyssal plain, basins (Figurel.l). Due to the uniqueness of these diverse habitats, a variety organism and biological activities occur in the Ocean floor. Habitat heterogeneity supports a variety of organisms and biological activity, these occur in the Ocean.

'Response o f Benthic community structure to the BaBitat Heterogeneity in Indian Ocean Introduction Chapter -1 _

Geomorphological features of the sea floor The seafloor topography is critically controlled by the ocean’s general circulation (Steven et al. 2004). It steers the ocean flows and also provides barriers that prevent the deeper water from mixing, except within deep passageways (Sarah et al. 2004). Based on bathymetry, ocean floor have been divided into 3 major provinces such as continental margin, deep- ocean basin and mid oceanic ridges by Thurman and Trujillo (1999).

Shelf break

However there are also other features present such as seamounts, trench, abyssal hills etc. (Figure 1.1). The deep sea, defined here as depths below the shelf break at, 200 m, is the largest ecosystem on the planet. The deep sea contains many of the distinct habitats, such as rocky mid-ocean ridges, submarine canyons, trenches, seamounts, island-like chemoautotrophic cold seeps, hydrothermal vents and whale-falls, and sediment-dominated continental slopes and abyssal plains (Gage and Tyler 1991). There are many unique ecological and geological settings which shapes the unique habitats in the deep-sea environment. Studies in deep seas began after Forbes’ dredging cruise in 1842. In the past 170 years twenty-two

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3 | P a g « Introduction Chapter -1

new deep-sea habitats and ecosystems have been discovered and an average of about 1 new habitat is being discovered every 8 years (Ramirez-Llodra et al. 2010) (Table. 1.1).

Table 1.1. Year of discovery of new habitats and/or ecosystems from Forbe’s Azoic Theory to date. OMZ - Oxygen Minimum Zone; MOR - Mid-Ocean Ridge (adopted from Ramirez- Llodra et al. 2010). Deep -sea habitat Year Reference Fine sediment (400 m) 1840 Forbes, 1844 Fine sediment (600 m) 1849 Sars, 1849 Fine sediment (2000 m) 1862 Jenkin, 1862 Submarine canyons 1863 Dana, 1863 Seamounts (geologic feature) 1869 Ankarcrona, 1869 Sponge fields 1870 Thomson, 1873 Open water 1876 Challenger Report, 1885 Fine sediment (abyssal) 1876 Challenger Report, 1885 Manganese nodules 1876 Challenger Report, 1885 Cold-water corals (as distinct ecosystem) 1922 Broch, 1922 OMZ pelagic 1925 Hentschel, 1936 OMZ benthic 1928 Spiess, 1928 Whale falls (as source of food) 1934 Krogh, 1934 Mud volcanoes 1934 Chhibber, 1934 Trenches 1948 Belyaev, 1989 Wood falls 1952 Galathea Report. 1956 MOR (as spreading ridges) 1963 Vine and Mathews, 1963 Back-arc basins 1971 Karig, 1971 MOR (fast spreading) 1977 Lonsdale, 1977 Xenophyophore fields 1979 Rice et al., 1979 Deep hypersaline anoxic basins 1983 Jongsma, 1983 Cold seeps 1984 Pauli et al., 1984 MOR (slow spreading) 1986 Rona et al., 1986 Whale falls (as chemosynthetic habitat) 1989 Smith et al., 1989 Brine pool (as chemosynthetic habitat) 1990 MacDonald et al., 1990 Asphalt habitat (Chapopote) 2004 MacDonald et al., 2004 Large bare rock region South Pacific 2006 Rea et al., 2006

Continental margins A relatively shallow area where the portion of the sea floor extends out from the continents and then drops down to connect with the deep seabed is called the Continental shelf (Churchill and Lowe 1999). The shelf is directly adjacent to the coast and slopes down gently until about 130 meters. The slope, which comes next and is steeper, dropping down sharply to about 1,200 to 3,500 meters; and rises, where the margin gradually merges with the deep seabed (Churchill and Lowe 1999). Together, these areas cover about one-fifth of the ocean floor. Continental margins are dynamic, heterogeneous setting formed by tectonic, terrestrial and oceanographic influences (Wefer et al. 2003).

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4 1 t * Introduction Chapter - 1

Abyssal floor The abyssal plain located at ~5,500 - 6,000 m depth, is the largest single environment on earth. Further, in some small areas of the oceans, the sea floor drops away again into steep trenches upto the depths of - 10-11 km. Although often portrayed as gently sloping continuums, the bottom topography of each of these areas is complex, with steep mountains and valleys much larger than any terrestrial habitat.

Mid-oceanic ridges The underwater mountain that consists of various mountain ranges are formed by plate tectonics called Mid-oceanic Ridge. Mid-oceanic ridges are the primary site of volcanic activity and the site of creation of new crust on the planet. This exert a major influence on the evolution of the solid earth, affect the composition of the ocean waters and support distinctive habitats like hydrothermal vent which create unique forms of life.

1.3 Benthic communities and their classification

The community of organisms that live on, or in, the bottom of a water body is known as “benthos”. The term “benthos” derived from ancient Greek ‘PsvGoq’ word which meaning “depth of the sea, bottom”. The term was introduced by the eminent German naturalist and artist Ernst Haeckel (1834-1919), who also introduced the term “ecology”. The structure of benthic community is complex. Based on the habitat, benthos is classified into soft-bottom and hard-bottom. Benthic communities also comprises of species differing in terms of their ecology, life strategies and body size. Benthic community includes a wide range of organisms from bacteria to plants (phytobenthos) and animals

'Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean

5 [ P a s’ e Introduction Chapter -1

(zoobenthos). It also distributed at the different levels of the food web. Benthic animals are generally classified according to size: microbenthos <0.063 mm, meiobenthos 0.063- 0.5 mm, macrobenthos > 0.5 - <2.0 or 3.0 mm and, megabenthos >3.0 mm. Benthic animals mostly invertebrates such as the well known groups like the worms (polychaetes and oligochaetes), mollusks (bivalves and gastropods) and crustaceans (amphipods, isopods and decapods). Benthic invertebrates can be differentiated by the position they occupy on or in bottom sediments: • Infauna - animals that live in sediments, almost all worms and bivalves belongs to this category. • Epifauna - organisms that live on the surface of bottom sediments; many crabs and gastropods are considered epifauna. • Hyper-fauna - animals that live in the water layer close to the sea bed;

Importance of benthos

Benthos acts as a major recycling agent of carbon, nitrogen and phosphorus in the oceans. They consume the dissolved organic matter and inorganic nutrients from the water column as well as sedimentary organic matter and convert them into invertebrate biomass. The nutrients released from the sediments due to bacterial degradation of organic matter diffuse and disperse fairly rapidly into the overlying water and influence the primary production, which triggers secondary production in the marine environment. Hence benthic organisms occupy the intermediate to lowest position in the marine food chain. The structural and functional diversity of benthos characteristically respond to natural and anthropogenic disturbances in an integrated and continuous manner. Hence they have been widely used for evaluating the

Response of Benthic community structure to the hahitat heterogeneity in Indian Ocean Introduction Chapter - 1

aquatic ecosystem health status (Rosenberg and Resh 1993; Ingole et al. 2009; Sivadas et al. 2010). Community characteristics such as abundance, richness, diversity, evenness and community composition can be monitored to determine whether the community is changing over time due to natural or human-caused impacts.

1.4 Role of habitat heterogeneity in structuring and maintaining the benthic diversity

Benthic organisms inhabit an area of sea bottom which extends from the supra littoral zone to the bottom of the deepest trench. Heterogeneous habitat is most important feature of the benthic environment. Habitat heterogeneity is often suggested as being important for stability of population, and promoted as a means to aid the conservation of species in terrestrial (Benton et al. 2003; Oliver et al. 2010) as well as marine (Levin and Dayton 2009; Menot et al. 2010) environment.

Continental margin The true extent of deep-sea biodiversity has been recognized since 1960s after Sanders et al. (1965) found that high diversity at continental slope than on the shelf or abyss (Hessler and Sanders 1967; Sanders 1968; Rex 1981) along the transects between southern New England and the Bermuda islands. According to Levinton (1995) “there is a regular change in benthic diversity from coast to abyssal plain. Species diversity of macroinvertebrates and fishes increases with depth, to a maximum just seaward of the continental rise, and then decreases with increasing distance towards the abyssal plain”. Earlier explorations on benthic ecological studies were mainly focused at understanding the mechanism that promotes high species richness, with greatest interests on process that operate at small spatial scales (reviewed in Snelgrove and Smith 2002), or the role of energy flux to structuring the benthic communities (Laubier and

'Response of Bent die community structure to the daBitat deterogeneity in Indian Ocean

7 11‘ a si e Introduction Chapter - i

Sibuet 1979). In recent years various scientific question appeared in relation with benthic diversity and habitat heterogeneity after the discovery of cold seep communities and was investigated in relation to tectonic, oil and gas development (Sibuet and Olu 1998; Sibuet and Olu-Le Roy 2003). The continental margins are the most geologically diverse components of the deep-sea floor and provide essential ecosystem function and services (Weslawski et al. 2004) and also supports high habitat heterogeneity (Levin and Dayton 2009; Menot et al. 2010; Levin et al. 2010). There is also available evidence for high genetic as well as species diversity along the continental slopes (Etter et al. 2005). In recent years there has been an increased research on the role of biodiversity in the ecosystem functioning and services along the continental margin. The Census of Marine Continental Margin Ecosystem (COMERGE) is one such programme (Menot et al. 2010). Approximately 30% of all organic matter remineralization, and thus nutrient recycling, occurs in the continental margin (Middelburg et al., 1997) which supports the high biodiversity in this area. Recent studies suggested that factors like depths, temperature, dissolved oxygen (DO) and overlying productivity influence the benthic community structure of the continental margin (Levin et al. 2000; Ingole et al. 2010; Levin et al. 2010a; Levin et al. 2010b; Hunter et al. 2012).

Deep-sea The deep-sea is the largest ecosystem in the planet with approximately 50% of the earth surface covered by ocean about 3000 m deep. Although this ecosystem supports one of the largest reservoirs of biodiversity on the planet, it is the least studied because of the remoteness and technological deficiency. The historical H.M.S Challenger expedition (1872-1876) marked as success story to discover the deep-sea communities in the world ocean for the first time. Sir John Murray (1890) commented after the Challenger Expedition that “It may be regarded as a well-established fact

'Response of Bent die community structure to tfie fiaBitat heterogeneity in Indian Ocean

8 | 1* a ii e Introduction Chapter -1

that the aggregate number of species and individuals is greater in the shallower zones of depth, and least in the greatest depths far removed from continental lands”. Since there was poor quantitative exploration of benthic diversity study in deep-sea until Sanders (1968) who showed that the biodiversity is higher than expected. Thereafter, number of quantitative studies has been carried out to confirm Sanders’ finding of high species diversity in the deep-sea (Grasslel972, 1989; Hessler and Jumars 1974; Jumars 1976; Gage 1979; Hecker and Paul 1979; Rowe et al. 1982; Grassle and Morse-Porteus 1987). Grassle and Maciolek (1992) estimated that the deep-sea is so diverse and unexplored that one new species can be found in every one square meter. Depth has major role structuring the benthic community in the ocean. Relationship of density and depth was found to be significant and negative for all the benthic groups (Rex and Etter 2010). With the exception of chemosynthetic sites such as hydrothermal vent and cold seep (Van Dover 2000, Tunnicliffe et al. 2003), life in deep-sea supported by organic inputs from the surface of the ocean through water column (Gage and Tyler 1991).Varieties of phenomena are responsible of nutrient input to the benthos such as community structure and organization (Rex et al. 2005), faunal composition (Carney 2005), life histories (Young 2003), trophodynamics (Rowe et al. 2003), body size (Thiel 1975), morphological diversity (McClain et al. 2004), and the potential for evolutionary diversification (Etter et al. 2005).

'Response ofBentBic community structure to the BaBitat Heterogeneity in Indian Ocean 9 I , t- Introduction C hapter - 1

1.5 Benthic research in Indian Ocean

Geography The Indian Ocean is located conventionally as an area between 25° N and 40° S and between 45° E and 115° E (Qasim 1998). It has a north-south extent of approximately 8490 km from northern boundary of Southern Ocean to the inner Bay of Bengal and spans 7800 km in east-west direction between southern Africa and western Australia. It spreads over 74.92 million km2 (29% of the global ocean 34 area) with an average depth of 3,873 m and a maximum depth of 7,125 m (Java Figure 1.2 Map of the Indian Ocean showing bathymetric features of the floor lenc ). (modified from General Bathymetry Chart of the Oceans-(GEBCO) World Ocean Bathymetry)

'Response o f benthic community structure to the habitat heterogeneity in Indian Ocean Introduction Chapter - i

History In the 60’s and 70’s of the 18th century, the science of biology was making rapid progress in the western countries. Wyville Thomson and Carpenter both well known biologist from England initiated the scientific research programmes on conditions of life and matter in the great oceans and seas of our globe. Photo source: Natural History Museum, History of Marine collection The famous voyage of H.M.S. ‘Challenger’ expedition received wide attention from scientists around the world, particularly amongst the biologists. In 1871 the voyage H.M.S. ‘Challenger’ carried out with less effort to explore the bottom fauna from Indian Ocean. After this expedition, another big survey ship was initiated at the Bombay Royal Indian Marine Dockyard. The ship was named ‘Royal Indian Marine Survey Ship Investigator’ (‘R.I.M.S.S Investigator’). In 1881 this ship sailed, though it was built for hydrographic and physiographic survey purpose, it was also used for collection of biological samples and thereafter exclusively used for biological survey. Zoologists collected priceless samples from during both the surveys which have been described by many zoologist and naturalists. Subsequently a number of expeditions were carried out in the Indian Ocean such as the German expedition Valdivia (1898-99), the Dutch expedition Siboga (1899-1900), the John Murrey expedition (1930-34), the Danish expedition Dana (1928-30), Galathea expedition (1950-52), Albatross (1950-52). The biggest expedition programmes ever in the history of India Ocean was the International Indian Ocean Expedition (HOE) during 1959-65. Ships from

Response of benthic community structure to the habitat heterogeneity in Indian Ocean

11 | P a g e Introduction Chapter - 1

several countries (Vema, Argo, Horizon, Pinoneer, Chain, Vega, Anton Brunn, Discovery, Challenger-II, Vityaz, Meteor Diamantina etc.) made significant contribution to the IlOE.

Benthic biodiversity Benthic samples have been collected from Indian continental shelf as well as deep Indian Ocean before the 1950s during several expeditions. The study was focused on megafauna and their taxonomic descriptions and hence lacked quantitative and ecological data. Majority of benthic communities research has been conducted in temperate, and to a lesser extent in the subtropical and boreal latitudes (Gray 1981). Although exploration on tropical continental shelf benthic study started in 1950 off the western edge of Africa (Buchanan 1957, 1958), there was no apparent increase in such studies until the middle of 1970s (Parulekar and Wagh 1975; Ansari et al. 1977; Harkantra et al. 1980, 1982; Parulekar et al. 1982; Warwick and Ruswahyuni 1987; Da Silva Attolini and Santo Tararam 2001; Dittmann 2002).This gap in knowledge of benthic studies in tropical region is due to many reasons including distance of major oceanographic centers from the tropics, logistics, efforts and lack of funding.

Neyman et al (1969) investigated the distribution patterns of the bottom fauna. A significant relationship found with surface phytoplankton, where the dead cells would rain down to the bottom, thus providing the food for bottom fauna. Due to high primary productivity, benthic standing stock was also observed to be higher at shallower depths (25-75 m) along the East African coast, Arabian peninsula and west coast of India. In contrast, benthic fauna found was extremely poor at 80-150 m depths because of low dissolved-oxygen content. Banse (1959) also reported an adverse effect of low-oxygenated bottom water on the demersal fisheries off

Response of BentBic community structure to tFie HaBitat Heterogeneity in Indian Ocean

12 | P a s e Introduction Chapter -1

Kerala coast. In India, two researcher Seshappa (1953) and Kurian (1953) were the first to carry out the detailed studies on the bottom fauna off Malabar and Travancore coast. Since then, numerous studies have been made along the east and west coasts of India to investigate the faunal associations at a community level of organization or to identify links to the key environmental factors (Ganapati and LakshmanaRao 1959; Radhakrishna and Ganapati 1969; Kurian 1971; Damodaran 1973; Ansari et al. 1977; Harkantra et al. 1980, 1982; Parulekar et al. 1982; Raman and Adiseshasail989). But all these studies did no unravel the question related to benthic community - environment relationship. After 1990’s, research on benthic community has been developed and investigated with some of the significant key environmental factors. Vizakat et al. (1991) studied the population ecology and diversity patterns of macroinvertebrates from Konkan, west coast of India. Venkatesh Prabhu et al. (1993) investigated macrobenthic community from nearshore sediments off Gangolli. Ansari et al. (1994) studied the macrobenthic assemblages interaction to harbor environment at Goa. Further, few quantitative and qualitative studies on macrobenthic assemblages and their interaction with local environments have been carried out from the western Indian shelf waters (Jayaraj et al. 2007; Jayaraj et al. 2008a and 2008b; Joydas and Damodaran 2009; Ingole et al. 2009; Sivadas et al. 2010). There are very few studies carried out to investigate the benthic fauna and their relationship to local environment on the continental slope areas of India (Ingole et al. 2010; Hunter et al. 2012). Moreover there are no quantitative studies on the seamount and mid-oceanic ridge benthos of India. Therefore, the present study aimed to investigate the benthic faunal assemblages and their ecosystem functioning with habitat heterogeneity from various geomorphological settings such as the western Indian continental margin, abyssal floor in Central Indian Ocean Basin, seamounts from Andaman back-arc Basin and mid-oceanic ridge of Carlsberg Ridge area.

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean Introduction Chapter -1

1.6 Objectives of the study

Macrobenthic fauna

Habitat: Continental margin and Abyssal region

• To investigate the taxonomic composition and abundance of macrofauna. • To analyze biomass size spectra • To study the relationship between the macrofauna and environmental variables. • Biogeographical boundary of OMZ macrofauna compared to other data. • Macrobenthic data will be discuss on local and regional scale

Megabenthic fauna

Habitat: Seamount and Ridge area

• Taxonomic composition of megafauna from seamount and Ridge area • Exploring the new underwater world- how many new species? And if so, are they endemic to the region? • How seamount communities differ within & between the habitat types on local as well as regional scale?

“Response of benthic community structure to the habitat heterogeneity in Indian Ocean Chapter 2 Macrofaunal community structure in western Indian continental margin including oxygen minimum zone McarofaunaC community structure in western Indian Continental margin

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2.1 Introduction

It is known that biodiversity changes with slope either on land or sea. This is

because of the altitude or a depth that harbors complex habitats which play a key role in generating the diversity throughout the slope.

The transition between thick continental crust and thin ocean crust is considered as continental margin. It is extending from the sublittoral to the abyssal zone, has various interesting habitats that can be described by geomorphological features (e.g shelf, slope, rise, marginal highs, etc.) and their related environmental conditions (e.g. depth, pressure, temperature, salinity, light, dissolved oxygen, sediment characters and other biogeochemical features). All of these features play an important role in generating and maintaining biodiversity along the continental margin. In the past few decades, considerable attention has been given to the study of continental margin biodiversity (Flach and Thomsen 1998; Tselepides et al. 2000; Palma et al. 2005). At present the deep continental margin is considered from 140 - 3,500 m extending over 320,000 km in length and covering approximately 40 million km' or approximately 11% of the total area of the ocean (Jahnke 2010; Menot et al. 2010). Over this depth range we find distinct hydrographic characteristics overlay the bottom, creating strong gradients in pressure, temperature, food availability and substrate stability, the intensity that can challenge any ecosystem on the planet. Seamounts, canyons, deep water coral reefs, muddy slopes are the major habitats that create flow conditions suitable for corals (Buhl-Mortensen and Mortensen 2004), sponges (Cook et al. 2008), cnidarians, and giant agglutinated protozoans (Levin 1991), and also methane-rich fluids from the crust in subduction zone support large siboglinid worms, clams, and mussels (Sibuet and Olu 1998; Etter et al. 2005) and many other protozoans and metazoans.

Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 15 | r a >4 e McarofaunaC community structure in western Indian Continental margin

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The western Indian continental margin, located in the eastern Arabian Sea of the northern Indian Ocean, represents a series of complex environments including a permanent, oxygen depleted zone. Although the Arabian Sea covers only 2% of the surface area of the World Ocean, it is one of the most biologically productive regions (Ryther and Menzel 1965), mainly due to the upwelling of nutrients during the summer, southwest monsoon and convective mixing during the winter, northeast monsoon (Madhupratap et al. 1996; Wiggert et al. 2005). The high biological productivity combines with slow re oxygenation to produce one of the most intense oxygen depletion zones observed anywhere in the open ocean (Swallow 1984; Naik and Naqvi 2002). This zone intercepts the continental margin at the shelf and continental slope (i.e. bathyal depths), creating extensive seafloor habitats subject to these extreme conditions, which have persisted for hundreds of thousands of years (Reichart et al. 1998). These oxygen-depleted zones are known as oxygen minimum zones (OMZs: defined by oxygen concentration <0.5 ml L'1). The OMZ in the Arabian Sea is spread over ~285,000 km2 of the benthic area. About 25% of the OMZ has an oxygen concentration < 0.5 ml L'1 and 30% of the area has an oxygen level of <0.2 ml L'1 (Helly and Levin 2004). This OMZ is the thickest found anywhere in the world and accounts for 40% of the global pelagic N2 production (Bange et al. 2005). According to recently published data, widespread open-ocean oxygen deficiency in this region results from the combination of a high oxygen demand arising from high biological productivity in the surface water and the limited supply of oxygen in intermediate waters (Jayakumar et al. 2009). This low concentration of dissolved oxygen (DO) has a major impact on biogeochemical processes such as the carbon and nitrogen cycles (Naqvi et al. 2006) and on benthic ecological functioning (Levin 2003).

The vertical distribution of benthic populations and their community structure is greatly influenced by the presence of OMZs (Rosenberg et al. 1983; Arntz et al. 1991; Levin 2003). The structure of macrofaunal communities in OMZs

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 16 ] t‘ -i >: c M e arofaunaC community structure in western IncCian ContinentaCmargin

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typically shows reduced diversity and high dominance in comparison with non-OMZ slope environments (Levin et al. 2001), although the patterns of faunal abundance are less consistent. Biomass is often reduced where oxygen levels are lowest because the macrofauna of the OMZs are generally dominated by small-bodied polychaetes, features likely associated with the low DO, the high availability of food and the reduction in predation pressure (Levin et al. 2002). Previous studies of open-ocean OMZ benthos have suggested a strong lower-boundary effect, with high densities of hypoxic- tolerant faunas aggregating in the lower part of the OMZ (Thompson et al. 1985; Levin 2003; Hughes et al. 2009).

Various geomorphological features occur on the western Indian continental margin. The shelf break in this region occurs between 80 m and 110 m, is wider in the northern shelf and narrows progressively towards the south. Various physical, chemical and geological processes control the sedimentation in this region. The sedimentary input is primarily from rivers that drain from the Western Ghats mountain range. Information on the benthos of the deep eastern Arabian Sea, especially from the Indian margin, however, is not available for global comparison. Neyman (1969) studied the benthos of the eastern Arabian Sea and suggested that bottom fauna is poor between 80 m and 150 m depth due to an inflow of subsurface water with low oxygen content. Earlier studies on the Indian shelf showed a definite correlation between macrofaunal standing stocks and organic carbon as well as the nature of the substrata (Parulekar and Wagh 1975; Harkantra et al. 1980). The community structure and abundance of nearshore and shallow-water macrofauna is reasonably well known (Jayaraj et al. 2007, 2008 a, b; Ingole et al. 2009; Joydas and Damodaran 2009). Most of these reports highlight the influence of environmental factors on the structure of the macrobenthic community. However, most studies were based on sampling at shallow (<200 m) depths in the shelf region. As a result, information on the benthos of the western Indian continental slope including the OMZ and deeper areas is not

“Response o f Bent Hie community structure to tHe Habitat Heterogeneity in Indian Ocean 1 7 11 .1 y r McarofaunaCcommunity structure in western Indian ContinentaCmargin

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available. Although Joydas and Damodaran (2013) studied the OMZ benthos in broader geographical range of the western Indian continental margin, but it was restricted to the shelf region only. Recently, benthic biological and biogeochemical process within the OMZ were investigated on the Pakistan Margin of the northern Arabian Sea (Levin et al. 2009; Hughes et al. 2009; Cowie and Levin 2009; Murty et al. 2009; Gooday et al. 2009) and from Indian continental margin (Ingole et al. 2010; Hunter et al. 2012).

Objectives

1) To generate regional biodiversity data that can be globally compared to other continental margins.

2) To study the sources of habitat heterogeneity from shallow- to deep-water regions.

3) To identify the environmental factors responsible for changing the macrofaunal community structure on the western Indian margin.

4) To analyze biomass size spectra.

It has been recognized that the environmental conditions of the eastern side are different from those acting on the western region of the Arabian Sea (Qasim 1982). Furthermore, the macrofaunal data show a striking contrast (especially through the OMZ core) between the western Oman margin and the eastern Pakistan margin of the northern Arabian Sea (Hughes et al. 2009). In recent studies, increased productivity has been reported from the Arabian Sea as well as the west coast of India (Madhupratap et al. 1996; Prasanna Kumar et al. 2000).

Thus, on the basis of previous studies, we hypothesize that:

1. Increased productivity of the Indian margin will be reflect in standing stocks that are higher than those on the Pakistan margin.

’Response of Benthic community structure to the habitat heterogeneity in Indian Ocean IS | r McarofaunaC community structure in western Indian ContinentaCmargin

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2. Macrofaunal abundance and biomass will be high and diversity will be relatively low in the OMZ region and low DO concentration will be responsible for changing the community structure at some depths.

2.2 Oceanographic settings of the study area

The surface area of the Arabian Sea, between latitudes 0° and 25° N and longitudes 50° and 80° E, is about 6.225 x 106km2. It is bound on the northern, eastern and western sides by the land masses of Asia and Africa. It is an area of negative water balance, where evaporation exceeds precipitation and runoff. The excess of evaporation over precipitation is highest (100 - 150 cm) off the Arabian coast and decreases steadily towards the southeast. A slight excess of precipitation over evaporation (<20 cm) occurs annually off the southwest coast of India (Venkateswaran 1956).

Surface circulation in the Arabian Sea is controlled by the seasonal variation in winds. Two types of winds blow from different directions and form two different monsoon seasons: the SW monsoon during summer (which leads to precipitation over the entire Indian peninsula) and the NE monsoon during winter. During the SW monsoon, biological productivity in the Arabian Sea lies mainly around the centers of seasonal upwelling off Arabian Peninsula, Somalia and southwest India (Qasim 1977). During this time, the upwelled waters on the southwestern margin of India are restricted by a thin (5 - 10 m) lens of low-salinity water, which originates from local precipitation and runoff from the narrow coastal plain that receives heavy rainfall (Stramma et al. 1996).

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 1 9 1 i* « « <■ McarofaunaC community structure in western Indian Continental margin

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Study area

A detailed benthic sampling programme was performed on board ORV Sagar Kanya during August 2007 (cruise no. SK 237) in order to generate local- scale benthic data in western Indian continental margin (Figure 2.1). At the transect of 14° N latitude, the shelf break is located about 105 km from the coast (~ 120 m depth), followed by a 116 km wide shelf margin basin. A mid shelf basement ridge, the dominant visible feature, divides the basin into eastern and western sections. The bottom topography in the mid-lower slope region is strewn with prominent flat-topped marginal highs (Rao and Veerayya 2000; Chakraborty et al. 2006). Topography of other transects are narrow shelf break towards to south, steep slope and wide basin excluding the marginal highs.

2.3 Materials and Methods

Thirty stations were sampled at water depths varied between 25 and 3150 m using a spade box corer (50 x 50 x 50 cm size) (Table 2.1a; Figure 2.1). Sub sampling was done with a PVC core (15 cm dia) and 1-3 subcores were taken from each box core. Separate sub-cores were collected for organic carbon (Corg), sediment chlorophyll-a (Chl-a) measurements and texture (grain sizes) analysis and frozen at -20°C. The water overlying the box core and sub-core sediment samples was sieved through a 300-pm mesh screen and then fixed and preserved using buffered 10% formalin to which rose Bengal was added. Bottom-water salinity and temperature data were collected using a CTD deployed down to 1524 m. CTD data from deeper depths could not be obtained due to technical problems. Below this depth, water was collected using Niskin bottles and was used for DO and Chl-a analysis. We did not check the bottom water DO for all the stations as it is known to be permanent OMZ occurs depths between 150-1250 m in the eastern Arabian Sea (Helly and Levin 2004).

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 2 0 1 P McarofaunaCcommunity structure in western Indian ContinentaCmargin

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Laboratory analysis and data processing

DO was analyzed by Winkler’s method (Strickland and Parsons 1968). Chl-n was estimated using an acetone extraction method (Holm-Hansen 1978). Total carbon analyses were carried out on the upper 2 cm of freeze-dried sediments using aNCS 2500 (Model- EA/NA1110) CNS analyzer. Inorganic carbon was analyzed by a CO2 Culometer analyzer and the percentage of CaC03 was calculated. Percentage of Corg was calculated by subtracting inorganic from total carbon. In the top 2 cm, sediment texture was determined by Malvern Laser Analyzer (Model - Hydro 2000MU) (Plate 2.1).

In the laboratory, the faunal samples were washed on a 300 pm sieve, sorted, identified and counted. Specimens were identified to the lowest possible taxon. At each site, the faunal counts from individual subcores (1 to 6 subcores from 1 transect, usually 2, box cores) were averaged and the mean value converted to no. m'2. The faunal counts from the water overlying the box core were divided by the number of subcores taken.

Biomass was determined by using the wet weight method after blotting. The biomass (shell on) was estimated similarly and converted to g.m' (wet weight). Biomass size-spectra (BSS) were calculated separately, pooling data from each station in terms of depth sub cores. The total BSS for each depth was determined by summing individual biomasses in each of the size classes. To facilitate comparison of the plotted spectra, the biomass in each class was converted to percentage of the total biomass for each depth (Hanson 1990). Due to less abundance of Mollusca in the faunal population, the shells on taxa were excluded during BSS analysis.

The data were subjected to univariate analyses to study the benthic community structure using Margalefs index (Margalef 1968) for species richness (d), Pielou’s index (Pielou 1966) for species evenness ( / ’), and the Shannon-Wiener index (Shannon & Weaver 1963) for species diversity (//'by using loge). The significance of the regions outlined a priori was tested with

:’Response o f benthic community structure to the habitat heterogeneity in Indian Ocean 2 1 11* -i i; McarofaunaC community structure in western Indian Continental margin

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multivariate analysis (Non-metric Multi-Dimensional Scaling (nMDS)) and the organisms that contributed most to the observed differences among groups were found by means of SIMPER (similarity percentage) using PRIMER 6 (Clarke and Warwick 1994). Linear regression between macrofaunal diversity indices and environmental variables was tested using STATISTICA 6. Feeding types were assigned to Annelida based on information in Fauchald and Jumars (1979).

2.3 Results

Environmental settings (Table 2.1a,b)

Water

The salinity of the bottom water did not vary at different depths, whereas temperature showed variations between the bathymetric gradients. Although bottom DO values were measured at all the depths of 14°N transect, due to technical problem DO for all station depths could not possible to measured. DO values were differed between the transects. OMZ phenomena appeared at 50 m depths of the shelf waters and persisted to lower boundary of upper slope and increased the DO values with increasing depths thereafter at 12°N (Figure 2.2). The bottom-water DO ranged from 0.08 to 2.3 ml l'1 at different sampling stations at 14°N transect. The lowest DO value was on the upper slope and increased from the lower slope reaching a peak in the basin area (Table 2.1b). The highest bottom-water Chl-a was in the shelf region (48 m) and the lowest value was observed on the upper slope. In general, the Chl-a was low at most of the stations (Table 2.1 a).

"Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 22 11* a « IMcarofaunaCcommunity structure in western Indian Continentafmargin

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Sediment

Four types of sediment textures were observed in the study area. The shelf region and upper slopes were characterized by silty and sandy facies, whereas the mid slope, lower slope and Arabian basin (Table 2.1a) were characterized by clayey silts. Sediment Ch\-a ranged from 0.15-2.1 pg g'1 and showed significant spatial variation. The middle slope showed the highest Chl-a, and the lowest values were recorded in the shelf (48 m depth) and basin (2556 m) region. Sediment Corg was high on the mid slope (4.37%) and a low value of 0.2% was observed at the basin station (2546 m). Organic carbon was high at stations with high silt content, which was the dominant sediment type in the study area.

Macrofaunal population structure: density, biomass and community composition

A total of 122 macro-invertebrate species from 5 major groups represented the macrofauna of the western Indian continental margin. Of the identified taxa, 83 (68.6%) were polychaetes, 22 (18.18%) crustaceans, 10 (8.27%) minor phyla and 6 (4.94%) others (e.g. Bivalvia, Arachnida and Oligochaeta).

Overall density showed high value at shelf area and decreased with increasing depth except few depths did not follow the trend such as 600 m and 2215 m at slope and basin respectively. The densities were ranged between 326 - 3722 ind m'2 (mean 1205 ± SD 809) in the study area. However biomass did not support and follow the similar trend of density. Overall biomass was observed high at upper to mid slope, moderate at shelf and lower at basin area. The mean biomass value ranged from 0.02 - 24.29 g m’2 (mean 2.39 ± SD 5.34).

Shelf

Six different depths were sampled at the shelf region. The average macrofaunal density gradually increased from shallow depths to deeper and

■ Response of benthic community structure to the habitat heterogeneity in Indian Ocean 23 1 a « IMcarofaunaC community structure in western Indian ContinentaCmargin

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showed highest pick at 102 m depth (Figure 2.3). The faunal density was highest at this region compare to other two regions. Mean (±SD) density was 2237 ± 1084 ind.m'2 at this region. The higher density (3722 ind.m'2) was observed at the depth 102 m while lower density (971 ind.m'2) recorded at 34 m depth. Mean (±SD) biomass was 3.62 ± 5.5 g.m" were highest (13.32 g.m' ) was measured at 102 m and lowest (0.17 g.m ') was at 25 m depth in this region (Figure 2.4).

Slope

13 different depths with various latitudes were sampled to population study of macrofauna from slope region. Mean (±SD) density was 1054 ± 592 ind.m’2. The highest faunal density (2200 ind.m’2) showed at 201 m depth while lowest (424 ind.m’ ) was in OMZ core (525 m) of this region (Figure 2.3). Mean (±SD) biomass was 3.61 ± 6.95 g.m’ where highest (24.29 g.m’ ) was recorded at 608 m and lowest (0.06 g.m’2) was at 1897 m depth (Figure 2.4).

Basin

11 different depths were sampled at basin region. Mean (±SD) density was 929 ± 568 ind.m’2 (Figure 2.3). The highest faunal density (2318 ind.m"2) was observed at 2215 m while lowest density recorded at 3001 m depth of this region. Mean (±SD) biomass was 0.29 ± 0.32 g.m’2 where highest (1.04 g.m’2) was recorded at 2546 m and lowest (0.03 g.m’ ) was at 2004 m depth (Figure 2.4) .

Biomass size spectra (BSS)

Biomass in body size classes varied significantly among the regions. In the shelf area, there was a biomass peak in the 500 - 1000 g weight class (Figure 2.5) , due to dominance of large size surface deposit feeder Paraprionospio pinnata and cirratulidae. In the slope area, surprisingly there was a biomass peak in the 1000 - 2000 g weight class, due to dominance of large bodied

"Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 24 | P n « IMcarofaunaCcommunity structure in western Indian ContinentaCmargin

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spionidae polychaeta. In the basin area, there was a biomass peak in the 300 - 500 g weight class, due to dominancy of cirratulids and oligochaetes.

Composition

The values for macrofaunal composition in different physiographical provinces are described below and are shown in Table 2.2.

Polychaeta was by far the dominant macrofaunal group at all the water depths (Figure 2.6). The maximum proportion (100%) of polychaetes was observed on the shelf (25 m), slope (201, 1001 and 1524 m) and basin (2443 m) while minimum (42.85%) was in the basin (2388 m). The next most abundant group was Crustacea with maximum relative abundance (57.14%) at 3150 m and minimum (1.9%) at 34 m depth. Further, other groups Oligochaeta, minor phyla and Bivalvia also contributed all three regions of the study area.

Shelf A total of 46 taxa were identified and Polychaeta was the dominant group, contributing to 85% - 100% of the faunal abundance. Of the 28 polychaete families identified in the entire area, 23 were observed on the shelf. The family Spionidae made the highest contribution (21.7%) followed by Paraonidae (19.8%) and Capitellidae (16.2%). Natantia and Oligochaeta were present but species of Amphipoda were not recorded. Other groups such as Bivalvia and minor phyla were found in low numbers.

Slope All five groups were present in this depth range. The majority (68 - 100%) of the macrofaunal animals were polychaetes, which were represented by 20 families. Overall Spionidae was the dominant group while Cirratulidae and Cossuridae were next in dominance. Spionidae occupied 38.14%, 19.4% and 57.4% at upper, mid and lower slope area, respectively. The maximum number of families (18) was observed in the lower slope area. Crustacea was

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 25 | P » MearofaunaCcommunity structure in western Indian Continentalmargin

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the second dominant group and mostly present in OMZ boundary at the mid slope to lower slope region.

Basin The highest number of taxa (81) was present in the basin region. This area was marked by a lower proportion (42.8 - 100%) of Polychaeta than the other two regions. A total of 24 polychaete families were observed, with the Spionidae, Cirratulidae and Paraonidae being dominant (28.2%, 20.1% and 16.9%, respectively). The highest contribution of Crustacea (57.1% at 3150 m) and minor phyla (24.9% at 2443 m) were also observed in this region. Tanaidacea was the most abundant group among the crustaceans, contributing to 14.6% to the total macrofaunal community in this region.

Dominant taxa

The three dominant species (representing 22 - 53% of the macrofaunal community) at their respective regions, together with their rank, are summarized in Table 2.3.

Among these species, the polychaetes Paraprionospio pinnata, Mediomastus sp. and Aricidea sp (Plate 2.2) were dominant and occupied first, second and third rank respectively at the shelf region. However, their faunal contribution decreased sharply as water depth increased.

Paraprionospio pinnata, Cossura sp. and Cirratulidae sp. 1 species dominated in the upper slope area. Mid slope was dominated by Paraprionospio pinnata, Paraprionospio sp. and Cirratulidae sp 2. The polychaete Prionospio sp. occupied the first rank while Paraprionospio pinnata and Syllis sp. were the next dominant at lower slope region.

The highest taxonomic diversity was observed in the basin. Here, Paraprionospio sp., Oligochaeta sp. 1 and Aricidea sp. were dominant. However, Tanaidaceans were also observed with high composition but did not get rank due to their variety in taxon. Tanaidaceans were also present on the

'Response o f benthic community structure to the habitat heterogeneity in Indian Ocean 26 j F a <■ e IMcarofaunaC community structure in western Indian Continentalmargin

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shelf and lower slope area but with low abundance and were absent on the upper and mid slope.

Multivariate (non-metric Multi Dimensional Scaling- nMDS) analysis of community structure

An nMDS plot based on the average abundance of macrofauna revealed three mixed group and three distinct groups at 15 - 24% similarity, reflecting majorly the different physiographic regions (Figure 2.7) in the study area. Although Group A was majorly contributed by all the shelf depths, three of upper slope (201, 367 and 525 m) and one of lower slope (1897 m) clustered with this region. This was due to Polychaetes Praprionospio pinnata, Cossura spl and Mediomastus sp. and contributed to ~76% similarity of Group A (Table 2.4). Group B also was not restricted within the regions. Five depths of slope (600, 608, 805, 1205 and 1993 m) and two depths of basin (2215 and 2454 m) formed Group B. This overlap was due to Polychaetes Cirralulus sp., Prionospio sp., Mediomastus sp., Praprionospio pinnata, Lumbrineridae sp.l and Glycera sp.l which contributed to more than 60% similar of Group B. The third group, Group D was made up of mid (1247) and lower slope (1633 m), and basin depths (2004, 2443 and 3150 m). the Polychaetes Praprionospio sp. and Aricidea sp.l contributed to the 90% similarity of this group. Due to 100% similarity of Polychetes P. pinnata, Aricidea sp.l and Nemertinia sp.2, Group C was restricted to the basin depths (2150, 2388 and 3001 m). Group E was combined with mid and lower slope depths (1001, 1005 and 1524 m), due to Cossura sp.l, Cirratulidae sp.2 and Maldinadea sp.l. The Group F was restricted to basin area only (2001, 2546 and 2556 m) which was found to 61% of species (Cirratulidae sp.3, Goniada sp and Tanaidacea sp.5) similarity between the depths.

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 27 |P a j McarofaunaCcommunity structure in western Indian ContinentaCmargin

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Diversity indices

Margalef s index (d) varied from 0.32 to 5.5 over the study area (Table 2.5; Figure 2.8). A higher d value was recorded from the basin (2001 m) than in the mid slope. Species evenness varied from 0.5 to 0.9, with the higher value recorded at a depth of 2338 m, rather than at a shallower depth (34 m) on the shelf. Values of H' varied from 0.9 to 3.4. The highest IT value was also observed in the basin (2001 m).

Distribution of polychaete feeding types

Overall surface deposit feeders, discretely motile and tentaculate (SDT) polychaetes were dominant along the continental margin (Figure 2.9). The frequency of SDT was 12 - 100% (11 - 33% at shelf, 12 - 60% at slope and 17 - 100% at basin) along the study area. Surface deposit feeders, motile and other structure (SMX), and carnivore, motile and jawed (CMJ) were the next dominant after SDT along the study area. However dominancy of feeding types differed with distinct physiographic regimes.

CMJ feeding type polychaetes were dominant at Shelf region followed by SMX and SDT. Upper slope was dominant by SDT feeding categories and followed by SMX and CMJ. Mid slope appeared to similar feeding type dominancy with shelf area as CMJ and followed by SMX and SMT (surface deposit feeder, motile, tentaculate). Lower slope and basin area were categorized by similar feeding types (SDT, SMX, SMT and CMJ).

Correlation of environmental and community parameters

The correlation between macrobenthic parameters and environmental variables were based on Pearson’s correlation analyses (Table 2.6). Macrofaunal biomass showed positive correlations with sediment Corg . Macrofaunal population density was negatively correlated with depths (p<0.05) and silts, and positively correlated with sand (p<0.05). The J values were negatively correlated with sediment Chl-a and positively with depths

’Response of Benthic community structure to the BaBitat heterogeneity in Indian Ocean 2 8 1 i* a t- McarofaunaCcommunity structure in western Indian ContinentaCmargin

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(p<0.05). Sessile, sub-surface deposit feeders feeding types polychaetes (BSX) showed positive correlations with sediment Chl-a (p<0.05). A negative correlation found between SDT feeding types and Corg. FDP feeding types showed positive correlations with sand and negative with silty sediments.

2.4 Discussion

Continental margins comprise only a small portion, about 20% of the global ocean area. However, 80% of the globally accumulated organic matter are buried here (Wollast 1998) and thus represent the major repositories of carbon in the ocean (Premuzic et al., 1982; Henrichs and Reeburgh 1987; Walsh 1991). The observed high values of sediment Corg on the slope, and low values in the basin region, were in agreement with previous studies of the western Indian margin. According to Rao & Veerayya (2000) diverse topographic features on the slope and the associated hydrodynamic processes play an important role in the enrichment of Corg- The lowest DO value was measured at the upper slope stations along the study area. Although DO values varied between the transects, based on DO concentrations, the OMZ was found to extend from a water depth of 50 m to 1001 m in the study area, with the core of the OMZ located at 525 m where the lowest DO value was recorded.

Macrofaunalpopulation structure: density, composition and biomass

Macrofaunal density increased from the shallow to the deeper region of the shelf, decreased to its lowest value in the core of OMZ and then increased towards the deeper region. Macrofaunal density in the western Indian OMZ core and the lower part of the OMZ were extremely low compared to all other OMZ margins studied to date, except for the Pakistan margin located on the northeastern side of the Arabian Sea (Table 6). Hunter et al. (2012) reported no evidence of macrofaunal population in OMZ core of western Indian margin. But they also reported relatively high density and biomass within

'Response of Bent Me community structure to the habitat heterogeneity in Indian Ocean 2 9 1)' « :.i t JvtcarofaunaC community structure in western Indian Continental margin

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OMZ boundary at 800 m. In contrast the density of the present study appeared low compared to density reported by Hunter et al. (2012) from OMZ of Indian margin which primarily differed due to inclusion of Nematodes fauna. They reported that Nematodes contributed to ~30% of macrofaunal density at 800 m and -60% at 1100 m which marked the differences with the present study. Because the present study considered the Nematodes as meiofauna and hence excluded during analysis. In the present study, low faunal density was observed on the slope at depths where DO concentrations was 0.08 and 0.28 ml L'1 while measurements of Chl-a and Corg were high. Levin et al. (2009) suggested that oxygen thresholds for macrofaunal abundance are -0.11 - 0.13 ml L'1 when the other conditions are favorable. It is possible that oxygen thresholds in the present study area are higher than on the Pakistan margin.

Among the polychaetes, spionids were highly dominant in the entire study area including the OMZ core. Polychaetes such as cirratulids, cossurids, and paranoids were the next dominant on the slope and basin regions. Spionids and cirratulids were also the dominant families within the OMZ on the upper slope (400 - 700m) off Oman (Levin et al. 2000) and at shallow shelf station (140 m), the lower OMZ boundary (1200 m) and below the OMZ (1850 m) on the Pakistan margin (Hughes et al. 2009). In contrast, cirratulids and oweniids were reported as the dominant group in lower boundary of OMZ in the western Indian margin (Hunter et al. 2012). This may be due to the influence of spatial and temporal heterogeneity on the benthic macrofaunal assemblages. In the present study, cossurids contributed majorly to the lower part of the OMZ (1001), although they were also present on the lower slope which is located just beneath the OMZ and thereafter. This polychaete family was abundant in the OMZ core (100 - 200 m) off Central Chile (Gallardo et al. 2004). Since these polychaetes are deposit-feeders (both surface and sub surface) their predominance may reflect food availability (e.g. sediment Corg and Chl-a) within the OMZ region. Paraonids were abundant at sites above and below the OMZ regions as well as the upper shelf and the basin. A

%espouse, of BentBic community structure to tfie BaBitat Beterogeneity in Indian Ocean 30 | P n <> e tMcarof aunaCcommunity structure in western Indian ContinentaCmargin

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Similar, abundance of paranoids were observed at 1850 m of the Pakistan margin (Hughes et al. 2009). The Cossuridae and Spionidae were important taxa where oxygen concentrations were lowest. Cossurids are common in many bathyal OMZs, including the Pakistan margin were they are present at depths of 940 m and 1200 m, areas of high Corg. Furthermore, the global bathyal data on benthic faunal abundance and biomass indicate a reduction in density at the OMZ core (Rosenberg et al. 1983; Mullins et al. 1985; Wishner et al. 1995) and an increase at the OMZ boundaries (Levin 2003). Macrofaunal biomass increased from 25 m to 102 m, then showed fluctuation between the depths and an erratic increase at 608 m and 1205 m before declining again from 1205 m to 3150 m. Previous studies from the shelf region (Harkantra et al. 1980; Parulekar et al. 1982; Harkantra 2004) reported higher biomass at the shelf stations. The differences noted may be due to the varied sampling methods including different types of gear, water depth and the sampling season. Moreover, all the previous studies sampled at shallower depths (<200m). Although the biomass in the present study was low, the values increased on the shelf from the shallower to the deeper regions, a pattern not reported in earlier studies (Kurian 1971; Parulekar and Dwivedi 1974; Ansari et al. 1977; Jayaraj et al. 2007, 2008b). The high benthic biomass at shallower depths in the shelf region may reflect higher food availability in the form of Corg and Chi-a. The supply of food to the sub-tidal benthic environment depends on the proximity to the shore and water depth (Levinton 1982). Sediment Chl-a at 34 m and 102 m was moderately high. Furthermore, biomass was higher at 102 m compared to shallower regions, due to the presence of Natantia and Arenicola sp. Although the highest Corg was recorded in the lower boundary (1001 m) of the OMZ, biomass was lower at this depth and was related to faunal abundance. Surprisingly, high biomass values were observed at 525 m, 608 m, 1205 m which were not reflected in the abundance. This was due to the presence of the large-sized polychaetes such as Spionidae, Cirratulidae and Onuphidae. However Levin’s (2003)

Hesjionse of Benthic community structure to the habitat heterogeneity in Indian Ocean 3 1 1 P :i McarofaunaC community structure in western Indian Continental margin

______Chapter - 2 hypothesized that small-bodied organisms, whose bodies have a greater surface area for gas-change, are more prevalent under conditions of persistent dysoxia (low oxygen). The bigger body size macrofauna (bivalve Nuculana bicupidata and the snail Nassarius vinctus) which were majorly contributed to the faunal biomass in the OMZ water off northern Namibia (Zettler et al. 2009). Zettler et al. (2009) suggested that due to distinct effect of functional prosperities in the sediments including availability of food was related to big size organisms in the OMZ region off northern Namibia. The possible reason for the large body size could be modified branchia which supports to intake sufficient oxygen during respiration process in the present study. In general, food availability remains a significant determinant of animal abundance and biogenic structure depth of assemblages evolving under permanent severe hypoxia (Levin et al. 2009). However the detail investigation is required in further to confirm the possible causes of the large body size organism present in the OMZ in western Indian continental margin. Biomass showed an increase thereafter from the lower boundary of the OMZ towards the deeper region.

Influence of habitat heterogeneity on macrofaunal community structure

The nMDS ordination based on the macrofaunal community clustered the sites into 3 mixed and 3 distinct groups representing three different bathymetric provinces. Group A comprised stations of the shelf, OMZ cores and lower slope region where opportunistic species such as Paraprionospio pinnata, Mediomastus sp., Cossura sp.l and Cirratulidae sp.l were dominant. These polychaete species were most abundant at a depth of 102, 201 and 525 m, where the DO concentration was low (<0.5 ml l'1). For most of these species, this tolerance of stressful conditions such as the low DO (<0.5 ml f 1) has been observed in the OMZs of the Oman margin and off central Chile (Levin et al. 2000; Gallardo et al. 2004). The polychaete P. pinnata which is known to

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 3 2 1 ,i « < tMcarofaunaC community structure in western Indian ContinentaCmargin

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tolerate low oxygen concentration (Gallardo et al. 2004), the dominance has also been reported within the OMZ off Concepecion (Palma et al. 2005). In addition, one particular morphological adaptation of this species, an expanded branchial structure has been observed only in the OMZ settings, specifically at the lowest level of oxygen concentration on the upper slope (Figure 2.10). Group E was restricted to the slope region (1001 m and 1524 m) where the sub-surface deposit feeding polychaetes Cossura sp.l, Cirratulidae sp.2 and Maldinadea sp. 1 predominated within the macrofaunal community. Although 1524 m was outside the OMZ, it was close to the OMZ boundary and the measured DO was not as high, nor as stable as the values measured at deeper stations. Group F, the most diverse group, was dominated by different taxa, including Cirratulidae sp.3, Goniada sp., Tanaidacea sp.5, Levinsenia sp.2 and Spionidae sp.2. This group was confined to the three deeper (basin) sites, of which the 2546 m region had a higher value of Corg (excluding those measured at the OMZ stations). The nature and variability of the organic matter supplied to the deep-sea floor influence the structure and function of the communities (Grassle and Morse-Porteous 1987). Tanaidacea are not very diverse in shallow waters but are well represented in the deep sea (Dojiri and Sieg 1997; Pavithran et al. 2007) where they are one of the most abundant taxa. Among the crustaceans, Isopoda and Amphipoda are also particularly abundant and diverse in the deep sea, where they are among the most typical members of the deep-sea benthic communities (Sanders et al. 1965; Brandt et al. 2007). The diversity of the Group F assemblage in the present study was comparable to that of ‘normal’ deep-sea habitats. Of the non-polychaete taxa, oligochaetes were found on the shelf, upper portion and just beneath the OMZ and basin area. Oligochaetes have been reported from the low-oxygen zone in a basin off Peru with partially laminated sediments (Levin et al. 2002). During the present study,

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 33 | p n <■ e McarofaunaC community structure in western Indian ContinentaCmargin

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macrofaunal diversity was generally higher at shelf and basin sites than on the slope reflecting the lower concentration of oxygen in the slope region. Although, due to deposit feeders found in area where organic matters are low, the bathymetric distribution of polychaete feeding types did not directly related to the amount of organic matter available in the sediments. Moreover, the proportion of carnivores was also found in slope areas where organic matters are high. This is also another reason to deposit feeders did show any relationship with sediment organic matter. It is hypothesised that family-level differences in trophic ecology and individual variation in feeding behaviour influence the feeding responses of deep-sea macrofaunal assemblages (Witte et al., 2003; Sweetman and Witte 2008a, b). In deep sea sediments, bulk OM uptake by the macrofauna is primarily driven by the feeding responses of the dominant taxonomic groups to POM sedimentation. In particular, deposit feeding polychaetes dominate macrofaunal uptake of POM at the bathyal continental margins (Sweetman and Witte, 2008a; Gontikaki et al., 2011,). In the present study surface and sub-surface deposit feeding (SMX and SDT) polychaetes are dominated in the basin region. The result of the present study suggests that macrobenthic community structure on the western Indian margin is not determined by a single factor, but instead is influenced by a combination of environmental factors. Discussing animal-sediment relationships, Snelgrove and Butman (1994) concluded that the complexity of soft-sediment communities may defy any simple paradigm with regard to any single factor controlling their settlement and colonization. The distribution of annelids within OMZs worldwide has been reviewed by Levin (2003), who has suggested the different patterns of community structure are due to changes o f hydrodynamic, bathymetric or geochemical factors rather than dissolved oxygen alone. Among the biological parameters, abundance and biomass positively correlated with sand and correlated negatively with silt. This is because the sand percentage was higher in shallow water, where higher faunal abundance and biomass were also

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 3 4 11* ,* e McarofaunaC community structure in western Indian Continental margin

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higher. Similarly, P. pinnata, Cossura sp. and Ancistrosyllis sp. were also observed in sandy sediment at low oxygen concentrations on the western Indian shelf (Jayaraj et al. 2008b). The increase of Chl-a, in both water and sediment, was related to the enhanced phytoplankton production in the study area.

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 35 | P a <• JHcarofaunaCcommunity structure in -western Indian ContinentaC marai Chapter - 2

Table 2. 2. Macrofaunal taxon list and density (ind.m'2) data from Western Indian Continental M argin

Shelf Famdy name Taxa Water depths (m) 25 50 34 48 102 Arenicolidae Arenicola sp 0 0 0 0 11 Capitellidae Capitellidae sp.l 0 0 0 0 0 Capitellidae sp.2 0 0 0 0 0 Mediomastus sp 571 82 28 0 860 Neomediomastus sp 0 82 0 0 23 Notomastus sp 0 0 0 0 0 Cirratulidae Cirratulus sp 0 163 0 79 68 Cirratulidae spl 82 489 9 11 192 Cirratulidae sp2 0 0 0 0 0 Cirratulidae sp 3 0 0 0 0 0 Cirriformia tentaculata 0 0 0 0 0 Tharyx sp 0 82 9 0 0 Cossuridae Cossura sp.l 0 0 0 0 317 Cossura sp.2 0 0 0 0 0 Dorvilleidae Dorvillea sp 0 0 0 170 0 Staurocephalus spl 0 0 6 0 0 Saturocephalus sp.2 0 0 0 238 0 Flabelligeridae Brada sp.l 82 0 0 79 0 Brada sp.2 0 0 0 0 0 Flabelligeridae spl 0 0 0 0 0

1lesjponse o f Benthic community structure to the habitat heterogeneity in Indian Ocean 39 | i’ a g e IMcaro faunaCcommunity structure in -western Indian ContinentaCmargin C h a p te r - 2.

Glyceridae Glycera sp 1 0 0 0 0 0 Glycera sp 2 0 0 0 11 11 Goniadidae Goniada sp 0 0 0 11 0 Hesionidae Hesione sp 0 0 0 0 0 Hesionidae spl 0 0 0 181 0 Lumbrineridae Lumbrineridae 1 0 0 0 0 0 Lumbrinereis sp.l 163 0 38 45 34 Lumbrinereis sp.2 0 0 0 0 0 Lumbrinereis sp.3 0 0 0 0 0 Magelonidae Magelona sp 0 0 0 11 57 Magelonidae spl 0 0 0 0 0 Maldanidae Axiothella sp 0 0 0 0 0 Maldanidae sp 1 0 0 0 0 0 Nephtyidae Nephtys sp 0 0 0 34 23 Nereididae Nereididae 0 0 0 0 0 Nereis sp 0 0 0 23 0 Onuphidae Onuphis emerita 0 0 0 11 23 Onuphis sp 0 0 0 0 0 Opheliidae Opheliidae spl 0 0 0 0 0 Ophelina acuminata 0 0 0 0 0 Polyophthalmus sp 0 0 0 0 0 Scoloplos sp 0 0 0 11 11 Paraonidae Aparaonis sp 0 0 0 0 0 Aricidea sp 1 82 0 613 68 385 Aricidea sp2 0 0 0 0 0

“Response of benthic community structure to the habitat heterogeneity in Indian Ocean 40 11* a g c M carofaunaCcommunity structure in -western Indian ContinentaCmargin C h apter - e

Levinsenia spl 82 0 0 634 147 Levinsenia sp2 0 0 0 0 0 Paraonidae sp2 0 0 0 0 0 Paraonidae spl 0 0 0 0 0 Phyllodocidae Phyllodoce sp 0 0 0 0 0 Pilargidae Ancistrosyllis constricta 0 0 0 158 226 Ancistrosyllis sp 326 0 9 23 23 Pisionidae Pisione sp 0 0 0 102 0 Poecilochaetidae Poecilochaetus sp 0 0 0 23 0 Sabellidae Chone sp 0 0 0 0 0 Jasmineira sp 0 0 0 0 124 Sabella sp 0 0 0 0 0 Sabellidae spl 0 0 0 0 0 Sigalionidae Sthenelais sp 0 0 0 0 0 Spionidae Heterospionidae sp.l 0 0 0 0 0 Paraprionospio pinnata 408 489 132 272 543 Paraprionospio polybranchiata 0 0 0 0 11 Paraprionospio sp 0 0 0 0 351 Spionidae sp.l 0 0 0 0 0 Spionidae sp.2 0 0 0 0 0 Spiophanes sp 0 0 0 0 0 Sternaspidae Sternaspis sp 0 0 47 45 0 Syllidae Syllidae spl 163 0 0 23 11 Syllidae sp2 0 0 0 0 0 Syllis sp.l 0 0 0 0 0

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 411 P :i g c McarofaunaCcommunity structure in western Indian ContinentaCmargin ______C h a p ter - 2

Syllis sp.2 0 0 0 181 11 Terebellidae Terebellidae sp.l 0 0 28 11 91 Terebellidae sp.2 0 0 0 0 0 Unidentified Polychaeta sp. 1 0 0 0 11 0 Unidentified Polychaeta sp.2 0 0 0 0 0 Unidentified Polychaeta sp.3 0 0 0 0 0 Unidentified Polychaeta sp.4 0 0 0 0 0 Unidentified Polychaeta sp.5 0 0 0 0 0 Unidentified Polychaeta sp.6 0 0 0 0 0 Unidentified Polychaeta sp.7 0 0 0 0 0 Unidentified Polychaeta sp.8 0 0 0 0 0 Unidentified Polychaeta sp.9 0 0 0 0 0 Amphipoda sp.l 0 0 0 0 34 Amphipoda sp.2 0 0 0 0 0 Unidentitified Bivalvia sp.l 0 0 0 0 0 Unidentitified Bivalvia sp.2 0 0 0 23 0 Unidentitified Bivalvia sp.3 0 0 0 0 0 Bryozoan 1 0 0 0 0 0 Caprellidae (amphipod) 0 0 0 0 0 Cumacea 0 163 0 0 0 Dendrostomus sp 0 0 0 0 0 Echiurida 0 0 0 0 11 Halacarid 0 0 0 11 0 Harpacticoid 0 0 0 0 0 Isopoda sp.l 0 0 0 23 0

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 42 11* a Jvlca.ro fa u n a C co m m u n ity strueCure in w e stern In d ia n C ontinent aCm arg in Chapter - 2

Isopoda sp.2 0 0 0 0 0 Isopoda sp.3 0 0 0 0 0 Nemertinia sp.l 0 0 0 0 0 Nemertinia sp.2 0 0 0 23 0 Oligochaeta sp.l 0 0 0 0 0 Oligochaeta sp.2 0 0 0 0 0 Oligochaeta sp.3 0 82 28 204 34 Phascolion sp 0 0 0 0 0 Unidentified Sipuncula sp.l 0 0 9 11 0 Unidentified Sipuncula sp.2 0 0 0 0 0 Unidentified Sipuncula sp.3 0 0 0 0 0 Unidentified Sipuncula sp.4 0 0 0 0 0 Aseudomorpha 0 0 0 0 0 Natantia 0 0 19 11 11 Tanaidacea sp.l 0 0 0 136 79 Tanaidacea sp.2 0 0 0 0 0 Tanaidacea sp.3 0 0 0 0 0 Tanaidacea sp.4 0 0 0 0 0 Tanaidacea sp.5 0 0 0 0 0 Tanaidacea sp.6 0 0 0 0 0 Tanaidacea sp.7 0 0 0 0 0 Tanaidacea sp.8 0 0 0 0 0 Tanaidacea sp.9 0 0 0 0 0 Tanaidacea sp.10 0 0 0 0 0 Tanaidacea sp.l 1 0 0 0 0 0

'Response o f benthic community structure to the habitat heterogeneity in Indian Ocean 43 11* 11 e, 0 McarofaunaCcommunity structure in -western Indian ConlvnentaCmaravn Chapter ~ j

Tanaidacea sp.12 0 0 0 0 3

Slope Family Taxa Water depths (m) Upper slope Mid slope Lower slope 201 367 525 600 608 805 1001 1005 1205 1247 1524 1633 1897 1993 Arenicolidae Arenicola sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Capitellidae Capitellidae sp.l 0 0 0 0 0 0 0 0 0 0 28 82 0 0 Capitellidae sp.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Mediomastus sp 0 163 0 82 326 82 0 0 82 0 0 82 0 0 Neomediomastus sp 0 0 0 82 0 0 0 0 0 0 0 0 0 0 Notomastus sp 0 0 0 0 82 0 0 0 0 0 0 0 0 0 Cirratulidae Cirratulus sp 0 0 0 245 245 0 0 0 82 0 0 0 0 82 Cirratulidae spl 571 0 0 0 0 0 0 0 0 0 0 0 0 0 Cirratulidae sp2 0 82 57 0 0 90 113 0 0 163 85 0 82 0 Cirratulidae sp 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Cirriformia 0 0 0 0 0 0 0 0 0 0 0 0 163 0 tentaculata Tharyx sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Cossuridae Cos sura sp.l 652 245 14 0 0 0 283 82 82 0 57 0 163 0 Cossura sp.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Dorvilleidae Dorvillea sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Staurocephalus sp 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Saturocephalus sp.2 0 0 0 0 0 0 0 172 0 0 0 0 0 0

:Response of benthic community structure to the habitat heterogeneity in Indian Ocean 44 | P IMc.arofa:unaCconvm:unity structure in -western Indian ContynentaCmarfiin C h a p ter - j

Flabelligeridae Brada sp.l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Brada sp.2 0 0 0 0 0 0 0 0 0 0 28 0 0 0 Flabelligeridae spl 0 0 0 0 0 0 0 0 0 0 85 0 0 0 Glyceridae Glycera sp 1 0 0 0 0 0 82 0 0 0 0 0 0 0 82 Glycera sp 2 0 0 0 0 0 0 0 0 0 0 85 0 0 0 Goniadidae Goniada sp 0 0 0 0 0 82 0 0 0 0 0 0 0 0 Hesionidae Hesione sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Hesionidae spl 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Lumbrineridae Lumbrineridae 1 0 0 0 82 82 82 0 0 0 0 0 0 0 0 Lumbrinereis sp.l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Lumbrinereis sp.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Lumbrinereis sp.3 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Magelonidae Magelona sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Magelonidae spl 0 0 14 0 0 0 0 0 0 0 0 0 0 0 Maldanidae Axiothella sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Maldanidae spl 0 0 0 0 0 0 57 0 0 0 28 0 0 0 Nephtyidae Nephtys sp 0 0 0 0 0 0 0 90 0 0 0 0 0 0 Nereididae Nereididae 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Nereis sp 0 0 0 0 0 0 0 0 82 0 0 0 0 0 Onuphidae Onuphis emerita 0 0 14 0 0 0 0 82 0 0 0 0 0 0 Onuphis sp 0 0 0 163 82 0 0 0 82 0 0 0 0 0 Opheliidae Opheliidae spl 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Ophelina 0 82 0 0 0 0 0 0 0 0 0 0 0 0 acuminata

"Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 45 | >’ n k o JvlcarofaunaCcommunity structure in -western Indian ContinentaCm argvn_ Chapter - 2

Polyophthalmus sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Scoloplos sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Paraonidae Aparaonis sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Aricidea spl 0 0 0 326 0 0 0 82 82 163 28 0 0 0 Aricidea sp2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Levinsenia spl 0 0 28 0 0 0 0 0 0 0 0 0 0 0 Levinsenia sp2 0 0 0 0 0 0 0 0 0 0 198 0 0 0 Paraonidae sp2 0 0 0 0 0 0 0 0 82 0 0 0 0 0 Paraonidae spl 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Phyllodocidae Phyllodoce sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Pilargidae Ancistrosyllis 0 0 0 0 0 0 0 0 0 0 0 0 0 0 constricta Ancistrosyllis sp 0 0 14 82 0 0 0 0 0 0 0 0 0 82 Pisionidae Pisione sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Poecilochaetidae Poecilochaetus sp 0 0 0 0 0 0 0 0 0 0 57 0 0 0 Sabellidae Chone sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Jasmineira sp 0 0 14 0 0 0 0 0 0 0 0 0 0 0 Sabella sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Sabellidae spl 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Sigalionidae Sthenelais sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Spionidae Heterospionidae 0 0 0 0 0 0 0 0 0 0 0 0 0 0 sp.l Paraprionospio 815 326 212 163 408 0 0 0 0 0 0 0 245 82 pinnata Paraprionospio 0 0 0 163 0 0 0 0 0 0 0 0 0 0 polybranchiata

'Response o f Benthic community structure to the habitat heterogeneity in Indian Ocean 46 | P ii r Jvlcaro faunaCcommunity structure in -western Indian CoritvneritaCmarfivn C h apter - 2

Paraprionospio sp 163 0 0 82 0 245 0 0 0 163 0 163 82 163 Spionidae sp.l 0 0 0 0 0 0 0 0 163 0 0 0 0 0 Spionidae sp.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Spiophanes sp 0 82 0 0 0 0 0 0 0 0 0 0 0 0 Sternaspidae Sternaspis sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Syllidae Syllidae spl 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Syllidae sp2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Syllis sp.l 0 0 0 0 0 0 0 9 0 82 0 82 0 245 Syllis sp.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Terebellidae Terebellidae sp.l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Terebellidae sp.2 0 0 0 0 0 0 0 0 0 0 28 0 0 0 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.l Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.2 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.3 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.4 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.5 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.6 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.7 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.8

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 47 | P a g e iMcarofcuunaCcommunity structure in -western Indian ContinentaCmar ain

Unidentified 0 245 0 82 0 82 0 0 82 0 0 0 0 0 Polychaeta sp.9 Amphipoda sp.l 0 0 57 0 0 0 0 0 0 0 0 0 0 0 Amphipoda sp.2 0 0 0 0 82 0 0 0 82 0 0 82 0 0 Unidentitified 0 0 0 0 0 172 0 0 0 0 0 0 0 82 Bivalvia sp.l Unidentitified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Bivalvia sp.2 Unidentitified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Bivalvia sp.3

B ryozoan 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Caprellidae 0 0 0 0 0 0 0 0 0 0 0 0 0 0 (am phipod) C um acea 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Dendrostomus sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Echiurida 0 0 0 0 0 0 0 0 0 0 0 0 0 0 H alacarid 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Harpacticoid 0 0 0 82 0 82 0 0 0 82 0 0 0 0 Isopoda sp.l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Isopoda sp.2 0 0 0 0 0 0 0 82 0 0 0 0 0 0 Isopoda sp.3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Nemertinia sp.l 0 245 0 245 0 0 0 0 163 0 0 0 0 0 Nemertinia sp.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Oligochaeta sp.l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Oligochaeta sp.2 0 82 0 326 0 0 0 0 0 82 0 0 0 0 Oligochaeta sp.3 0 0 0 0 0 0 0 0 0 0 0 0 0 0

'Response o f Benthic communit y structure to the habitat heterogeneity in Indian Ocean 48 ( P n g e IMcarofaunaCcommunity structure in -western IncCicm. ContvnentaCmargin Chapter - 2

Phascolion sp 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Unidentified 0 0 0 0 0 0 0 0 0 0 0 Sipuncula sp.l 0 0 0 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 Sipuncula sp.2 0 0 Unidentified 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Sipuncula sp.3 Unidentified 0 82 0 0 0 82 0 0 0 0 0 0 82 0 Sipuncula sp.4 Aseudomorpha 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Natantia 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.4 0 0 0 0 0 0 0 0 0 0 0 0 0 163 Tanaidacea sp.5 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.6 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.10 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.ll 0 0 0 0 0 0 0 0 0 82 0 0 0 0 Tanaidacea sp.l2 0 0 0 0 0 0 0 0 0 0 0 0 0 0

"Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 49 | ]’ n r c JvlcarofaunaCcommunity structure in -western Indian ContinentaCmargin C h apter - 2

Basin Family Taxa Water depths (m) 2001 2004 2150 2215 2388 2443 2454 2546 2556 3001 3150 Arenicolidae Arenicola sp 0 0 0 0 0 0 0 0 0 0 0 Capitellidae Capitellidae sp.l 0 0 0 0 0 0 0 0 0 0 0 Capitellidae sp.2 9 0 0 0 0 0 0 0 163 0 0 Mediomastus sp 0 0 0 167 0 0 0 0 0 0 0 Neomediomastus sp 0 0 0 0 0 0 0 0 0 0 0 Notomastus sp 0 0 0 0 0 0 0 9 0 0 0 Cirratulidae Cirralulus sp 0 0 0 86 0 0 82 0 0 0 0 Cirratulidae spl 0 0 0 0 0 0 0 0 0 0 0 Cirratulidae sp2 0 0 0 0 0 0 245 0 0 0 0 Cirratulidae sp 3 57 163 0 245 0 0 0 66 82 0 0 Cirriformia 0 0 0 0 0 82 0 0 0 0 0 tentaculata Tharyx sp 0 0 0 82 0 0 0 0 0 0 0 Cossuridae Cossura sp.l 0 0 0 0 0 0 0 0 0 0 0 Cossura sp.2 0 0 163 0 0 0 0 0 0 0 0 Dorvilleidae Dorvillea sp 0 0 0 0 0 0 0 0 0 0 0 Staurocephalus sp 1 0 0 0 0 0 0 0 0 0 0 0 Saturocephalus sp.2 0 0 0 0 0 0 0 0 0 0 0 Flabelligeridae Brada sp.l 0 0 0 0 0 0 0 0 0 0 0 Brada sp.2 19 0 0 0 0 0 0 0 0 0 0 Flabelligeridae spl 0 0 0 0 0 0 0 0 0 0 0 Glyceridae Glycera sp 1 0 0 0 0 0 0 82 0 0 0 0

%espouse of Benthic community structure to the haBitat heterogeneity in Indian Ocean 50 | r o£9“J- Paraonidae Nephtyidae Opheliidae Nereididae Onuphidae Magelonidae Lumbrineridae Maldanidae Hesionidae Goniadidae Maofuna c t tucur i -etr ndi i nt gin rg a m C ta en tin n o C n ia d In -western in re ctu stru ity n u m m co aC n SMcaro fau Aricidea Levinsenia Aricidea Aparaonis Axiothella Scoloplos Polyophthalmus Nereis Nephtys Nereididae Magelona Opheliidaespl Maldanidaespl Magelonidaespl Lumbrinereis Hesione Ophelina Ophelina acuminata Lumbrinereis Lumbrineridae 1 Onuphis emerita Lumbrinereis Hesionidaespl Onuphis Goniada Glycera R sos eti omnt tutr t te aia htrgniy nIda Ocean Indian in heterogeneity habitat the to structure community f Benthic o “Response sp sp sp2 sp sp sp2 spl sp sp sp sp sp spl sp.3 sp.2 sp. 1 sp 28 28 28 19 19 0 0 0 0 9 9 0 0 0 0 0 0 0 9 0 0 9 0 0 0 82 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 163 82 82 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 167 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 82 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 11p » e 1 » a 51 p 38 75 57 19 9 9 0 0 0 9 0 0 0 9 0 0 0 0 0 9 9 0 0 0 0 ~ 82 r~ fa e - 2 - ter Cflap 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ^ 82 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ^ 163 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 M ca .ro faunaCcommunity s tr u c tu r e in -western Indian ContinentaC'marfiin Chapter 2

Levinsenia sp2 47 0 0 0 0 0 0 9 0 0 ~6~ Paraonidae sp2 0 0 0 0 82 0 0 0 0 0 0 Paraonidae spl 75 0 0 0 0 0 0 0 0 0 0 Phyllodocidae Phyllodoce sp 38 0 0 0 0 0 0 0 0 0 0 Pilargidae Ancistrosyllis 0 0 0 0 0 0 0 0 0 0 0 constricta Ancistrosyllis sp 0 0 0 171 0 0 0 9 0 0 0 Pisionidae Pisione sp 0 0 0 0 0 0 0 0 0 0 0 Poecilochaetidae Poecilochaetus sp 0 0 0 0 0 82 0 0 0 0 0 Sabellidae Chone sp 9 0 0 0 0 0 0 0 0 0 0 Jasmineira sp 0 0 0 0 0 0 0 0 0 0 0 Sabella sp 0 0 0 0 0 0 0 9 0 0 0 Sabellidae spl 19 0 0 0 0 0 0 28 0 0 0 Sigalionidae Sthenelais sp 0 0 0 0 0 0 0 19 0 0 0 Spionidae Heterospionidae sp.l 0 0 0 0 0 82 0 0 0 0 0 Paraprionospio 0 0 245 163 163 0 0 9 0 82 0 pinnata Paraprionospio 0 0 0 0 0 0 0 0 0 0 0 polybranchiata Paraprionospio sp 28 245 0 82 0 82 82 160 0 0 82 Spionidae sp. 1 0 0 0 0 0 0 0 0 0 0 0 Spionidae sp.2 94 0 0 0 0 0 0 47 0 0 0 Spiophanes sp 19 0 0 0 0 0 0 0 0 0 0 Sternaspidae Sternaspis sp 9 0 0 0 0 0 0 38 0 0 0 Syllidae Syllidae spl 0 0 0 0 0 0 0 0 0 0 0 Syllidae sp2 9 0 0 0 0 0 0 66 0 0 0

Hesjjonse of Benthic community structure to the habitat heterogeneity in Indian Ocean 52 [ P n g e M carofaunaf community structure in -western Indian ContinentaCmargin C h apter -

Syllis sp.l 0 0 0 0 0 0 0 0 0 0 0 Syllis sp.2 9 0 0 86 163 0 0 9 82 0 0 Terebellidae Terebellidae sp.l 0 0 0 0 0 0 0 0 0 0 0 Terebellidae sp.2 9 0 0 0 0 0 0 38 0 0 0 Unidentified 0 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.l Unidentified 38 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.2 Unidentified 47 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.3 Unidentified 38 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.4 Unidentified 19 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.5 Unidentified 47 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.6 Unidentified 19 0 0 0 0 0 0 9 0 0 0 Polychaeta sp.7 Unidentified 47 0 0 0 0 0 0 0 0 0 0 Polychaeta sp.8 Unidentified 0 0 0 82 0 0 82 0 0 0 0 Polychaeta sp.9 Amphipoda sp.l 47 0 0 0 0 0 0 28 0 0 0 Amphipoda sp.2 0 0 0 0 0 0 0 0 0 82 0 Unidentified 0 0 0 82 0 0 0 0 0 0 0 Bivalvia sp.l Unidentified 0 0 0 0 0 0 0 0 0 0 0 Bivalvia sp.2

Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 53 | V u McarofaunaCcommunity structure in -western Indian ConlinentaCmargin Chapter - -j

Unidentitified 28 0 0 0 0 0 0 28 0 0 Bivalvia sp.3 0 Bryozoan 1 0 0 0 0 0 0 0 0 0 0 82 Caprellidae 0 0 0 0 0 0 0 0 82 0 (amphipod) 0 Cumacea 0 0 0 0 0 0 0 0 0 0 0 Dendrostomus sp 38 0 0 0 0 0 0 0 0 0 0 Echiurida 0 0 0 0 0 0 0 0 0 0 0 Halacarid 0 0 0 0 0 0 0 0 0 0 0 Harpacticoid 0 0 245 163 0 0 0 0 0 0 82 Isopoda sp.l 0 0 0 0 0 0 0 0 0 0 0 Isopoda sp.2 0 0 0 0 0 0 0 0 0 0 0 Isopoda sp.3 0 0 0 0 0 0 0 47 0 0 0 Nemertinia sp. 1 0 0 0 0 0 0 0 0 0 0 0 Nemertinia sp.2 38 0 163 0 82 0 82 28 0 0 0 Oligochaeta sp.l 0 0 0 579 0 0 163 0 0 0 0 Oligochaeta sp.2 0 0 0 0 0 0 0 0 0 0 0 Oligochaeta sp.3 0 0 0 0 0 0 0 0 0 0 0 Phascolion sp 9 0 0 0 0 0 0 0 0 0 0 Unidentified 28 0 0 0 0 0 0 9 0 0 0 Sipuncula sp. 1 Unidentified 19 0 0 0 0 0 0 0 0 0 0 Sipuncula sp.2 Unidentified 19 0 0 0 0 0 0 0 0 0 0 Sipuncula sp.3 Unidentified 0 0 0 82 0 0 0 0 0 0 0 Sipuncula sp.4

■ Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 54 11> n r e McarofcamaCcommunity structure in -western Indian Continentahmargin Chaplet

Aseudomorpha 0 0 163 0 0 0 0 0 0 0 o N atantia 0 0 0 0 0 0 0 0 0 0 o Tanaidacea sp.l 0 0 0 0 0 0 0 0 0 0 o Tanaidacea sp.2 0 0 0 0 163 0 0 0 0 0 0 Tanaidacea sp.3 0 0 0 0 163 0 0 0 0 0 0 Tanaidacea sp.4 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.5 151 0 0 0 0 0 0 198 0 0 0 Tanaidacea sp.6 0 0 0 0 0 0 0 0 0 0 245 Tanaidacea sp.7 0 0 0 0 0 0 0 0 0 82 0 Tanaidacea sp.8 H 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.9 0 0 0 86 0 0 0 0 0 0 0 Tanaidacea sp.10 0 0 0 0 0 0 0 0 82 0 0 Tanaidacea sp.l 1 0 0 0 0 0 0 0 0 0 0 0 Tanaidacea sp.l2 0 163 0 0 0 0 0 0 0 0 0

■ Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 55 | P a g o Table 2.3. Rank wise dominant taxon along the study area Taxon Shelf Slope Basin Upper Mid Lower Paraprionospio pinnata 1 1 1 2 Mediomastus sp 2 Aricidea sp.l 3 3 Cossura sp. 1 2 Cirratulidae sp.l 3 Paraprionospio sp 2 1 1 Cirratulidae sp.2 3 Syllis sp 3 Oligochaeta sp.l 2

"Response of Bent file community structure to tfie haBitat heterogeneity in Indian Ocean 56 | V Table 2.4 Macrofaunal diversity along the western Indian continental margin

Depths (m) s d J H' Shelf 25 9 1.055547 0.877759 1.928634 50 8 0.946379 0.85698 1.78204 34 12 1.599216 0.563515 1.400281 48 34 4.13791 0.806036 2.842374 102 28 3.283864 0.766226 2.553223 Slope 201 4 0.38978 0.916851 1.271026 367 10 1.216801 0.935822 2.15481 525 9 1.322248 0.742429 1.631284 600 14 1.689066 0.942356 2.486931 608 7 0 .8 3 6 4 2 1 ' 0.882398 1.717068 805 10 1.289086 0.957417 2.204535 1001 3 0.327073 0.819448 0.900256 1005 7 0.938887 0.921372 1.792908 1205 11 1.435572 0.980727 2.351681 1247 7 0.895052 0.969576 1.886707 1524 11 1.524128 0.903967 2.167617 1633 5 0.645925 0.969715 1.560696 1897 6 0.745873 0.946412 1.695743 1993 8 1.016573 0.951796 1.979205 Basin 2001 40 5.472575 0.923215 3.405629 2004 4 0.462933 0.95282 1.320888 2150 8 0.975824 0.96854 2.014023

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 5 7 1 v a « 2215 15 1.806735 0.916542 2.482041 2388 6 0.745914 0.975615 1.748067 2443 4 0.51838 1 1.386294 2454 8 1.029594 0.948437 1.972218 2546 31 4.27696 0.857644 2.94514 2556 6 0.787788 0.975504 1.747868 3001 4 0.51838 1 1.386294 3150 5 0.617245 0.928383 1.494175

Table 2.5. SIMPER analysis of macrofaunal abundances along the study area (average abundances (Av. Abund), average Similarity (Av. Sim), similarity standard deviation (sim/SD), contributed percentage (Contrib.%) and cumulative contribution (Cum%) Group A (Average similarity: 24.69) Species Av.Abund Av.Sim Sim/SD Contrib% Cum.% Paraprionospio 382.37 15.39 2.63 62.36 62.36 pinnata Cossura sp. 1 154.5 1.93 0.47 7.8 70.16 Mediomastus sp 189.25 1.54 0.4 6.23 76.39 Cirratulidae spl 150.49 1.53 0.34 6.21 82.59 Aricidea spl 127.43 0.92 0.31 3.73 86.33 Cirratul idae sp2 24.4 0.59 0.29 2.4 88.72 Levinsenia spl 98.94 0.45 0.41 1.81 90.53 Group B (Average similarity: 24.12) Species Av.Abund Av.Sim Sim/SD Contrib% Cum.% Cirratul us sp 117.04 4.72 1.27 19.58 19.58 Paraprionospio sp 93.17 3.17 0.76 13.15 32.73

'Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 58) f* a £ c Mediomastus sp 105.38 2.78 0.87 1 1.54 44.27 Unidentitifed 58.21 2.75 0.87 11.4 55.68 Ploychaeta sp.2 Prionospio pinnata 116.45 2.03 0.59 8.44 64.11 Lumbriconeridae 1 46.58 1.78 0.6 7.38 71.5 Glycera sp. 1 34.94 1.19 0.4 4.91 76.41 Bivalvia sp.l 47.8 0.84 0.39 3.49 79.9 Aricidea sp. 1 82.08 0.82 0.39 3.4 83.3 Onuphis sp 46.59 0.79 0.39 3.27 86.57 Ancistrasyllis sp 47.73 0.65 0.39 2.7 89.27 Group D (Average similarity: 25.0J0 Species Av.Abund Av.Sim Sim/SD Contrib% Cum.% Paraprionospio sp 146.75 18.13 3.19 72.31 72.31 Aricidea sp. 1 81.52 4.58 0.58 18.28 90.58

Group E (Average similarity: 19.28) Species Av.Abund Av.Sim Sim/SD Contrib% Cum.% Cossura sp. 1 140.3 11.33 3.07 58.76 58.76 Cirratul idae sp2 65.99 4.88 0.58 25.3 84.06 Maldanidae spl 28.28 1.63 0.58 8.43 92.49 92.49 Group C (Average similarity: 19.12) Species Av.Abund Av.Sim Sim/SD Contrib% Cum.% Paraprionospio 163.02 13.22 4.65 69.16 69.16 pinnata Aricidea sp. 1 81.53 3.33 0.58 17.43 86.59 Nemertinia sp.2 81.52 2.56 0.58 13.41 100 Group F (Average similarity: 24.95 ) Species Av.Abund Av.Sim Sim/SD Contrib% Cum.%

’Response o f Bent die community structure to tFie BaBitat Beterogeneity in Indian Ocean 5911' a - !« Cirratul idae sp.3 68.03 6.29 4.13 25.187 25.18 Goniada sp 61.74 4.83 1.34 19.32 44.5 Tanaidacea sp.5 1 1 6 .2 7 4 .2 7 0 .5 8 17.08 61.58 Spionidae sp.2 47.14 1.33 0 .5 8 5.34 66.91 Syllis sp.2 33.46 0.99 5.93 3.95 7 0 .8 6 Amphipoda sp. 1 25.14 0 .8 0.58 3.2 7 4 .0 6 Bivalvia sp.3 18.86 0 .8 0.58 3.2 77.27 Lumbriconereis sp2 28.28 0 .8 0.58 3.2 80.47 Nemertinia sp.2 22 0 .8 0.58 3.2 83.67 Paraprionospio sp 62.85 0 .8 0.58 3.2 86.87 Nereis sp 18.86 0.53 0.58 2.13 89.01 Sabellidae spl 15.71 0.53 0.58 2.13 91.14

'Response o f bent Flic community structure to the fiaBitat heterogeneity in Indian Ocean 60 | f* n % <• Table 2.6. Correlation between biotic and abiotic parameters in thestucly area

D ep th TOC S ed C h i a C la y S ilt S a n d s -0.141 p=.457 -0.1298 p=.494 -0.0794 p=.677 0.2114 p=.262 -0.2143 p=.256 0.1331 p=.483 B io m a ss -0.3124 p=.093 0.2832 p=.129 0.0358 p=.851 0.2243 p=.233 -0.1716 p=.365 0.0914 p=.631 N -0 .4 7 4 5 p = .0 0 8 0.0164 p=.931 0.0309 p=.871 -0.2216 p=.239 -0 .6 3 2 5 p = .001 0 .6 2 7 P = 0.001 D -0.1036 p=.586 -0.133 p=.484 -0.0794 p=.676 0.2541 p=. 175 -0.1593 p=.400 0.0721 p=.705

J 0 .5 9 5 4 p = .0 0 1 -0.285 p=.127 -0 .3 6 2 8 p = .0 4 9 -0.1403 p=.459 0.2207 p=.241 -0.1578 p=.405 H' -0.0265 p=.890 -0.1008 p=.596 -0.1057 p=.578 0.1851 p=.328 -0.1313 p=.489 0.0664 p=.728

BMX -0.2194 p=.244 0.0275 p=.885 0.1053 p=.580 -0.0045 p=.981 -0.3311 p=.074 0.2969 p=. 111

BSX -0.1846 p=.329 0.3584 p=.052 0 .5 1 8 5 p = .0 0 3 0.203 p=.282 0.2863 p=. 125 -0.3122 p=.093

CDJ 0.2656 p=. 156 -0.1297 p=.494 -0.0723 p=.704 0.0792 p=.678 0.0025 p=.989 -0.0241 p=.900

CMJ 0.099 p=.603 0.1578 p=.405 0.1108 p=.560 0 .3 8 4 5 p = .0 3 6 0.0788 p=.679 -0.1769 p=.350 CMS 0.1161 p=.541 -0.1344 p=.479 -0.1539 p=.417 0.2541 p=.175 0.1462 p=.441 -0.2011 p=.287 FDP -0.2462 p=.190 -0.0098 p=.959 -0.0292 p=.878 -0.2371 p=.207 -0 .3 6 3 2 p = .0 4 9 0 .3 9 0 4 p = .033

FST -0.2261 p=.230 0.2808 p=.133 -0.0184 p=.923 0.0777 p=.683 -0.2869 p=. 124 0.2351 p = .211 II SDF -0.3513 p=.057 0 .3 7 8 8 p = .0 3 9 0.3417 p=.065 0.0669 p=.725 -0.0165 p= 931 -0.0037 00

SDT 0.1369 p=.471 -0 .3 8 p = .0 3 8 -0.3554 p=.054 -0 .3 9 7 2 p = .0 3 0 -0.1368 0 0.2322 p=.217 SMJ -0.0896 p=.638 0.2578 p=. 169 0.0981 p=.606 0.2145 p=.255 -0.029 p=.879 -0.0334 p=.861 SMT -0.1726 p=.362 0.0224 p=.906 0.0994 p=.601 0.0629 p=.741 -0.0864 p=.650 0.0599 p=.753 SMX 0.1798 p=.342 -0.0666 p=.726 -0.1488 p=.433 -0.1375 p=.469 0.2028 p=.283 -0.1432 p=.450

♦values in bold are significant

'Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 61 | P Me ar ofaunaC community structure in western Indian Continental margin

______Chapter - 2

mm!lii?§!iSfiLP Figure 2.1. Map showing stations location in the study area with respect to bathymetric gradients and legends indicating the sample collected depth range; 3D map also showing the stations locations with better view about the study area.

Response of benthic community structure to tlie habitat heterogeneity in Indian Ocean 62 | McarofaunaC community structure in western Indian Continental margin

______Chapter - 2

4:------DO (ml/L)

Figure 2.2. Dissolved oxygen concentration values measured by DO sensor attached with CTD along the water depths at 11°N and 12°N latitude of western Indian continental margin

"Response of benthic community structure to the habitat heterogeneity in Indian Ocean 63 | McarofaunaCcommunity structure in western Indian ContinentaCmargin

______Chapter - 2

Density (individuals/m*2)

500 1000 1500 2000 2500 3000 3500 4000 __i__ _1_ -25 -34 ■AS -50

- -102

- -201 -367 -525 -600 ■608 -805 -1001 -1005 -1205 -1247 -1524 -1633 -1897 -1993 -2001 -2004 -2150 -2215 -2388 -2443 -2454 -2546 -2556 V -3001 - -3150

Bagalkot

H u b ii H

C- Chilrmagalui Turrit ui 3 O 3 H«s5*n Ba {Be 111 ll Mysore • KFRAI.A' [Calicut* Coimbatore* Tiidjw ■S 3 0 Bodmayakkan Corhin*

Alltffiev kajafW.!

UteHAP'-VEFF Trivan dn

Figure 2.3. Depth as well as region-wise macrofaunal density and distribution map along the study area

:Response of benthic com m unity structure to the habitat heterogeneity in Indian Ocean 64 | McarofaunaCcommunity structure in western Indian Continentalmargin

______Chapter - 2

Biomass (g.m 2)

Figure 2.4. Depth-wise macrofaunal biomass and distributional map along the study area

•Response of benthic community structure to the habitat heterogeneity in Indian Ocean 65 1 Rsos ofBnhccmmnt tutr t tehbtt eeoeet i nin Ocean Indian in heterogeneity habitat the to structure munity com f Benthic "Response o marobenthic assemblages in the study area study the in assemblages marobenthic Figure 2.5. 2.5. Figure Biomass occurrence percentage __ McarofaunaCcommunity structure in western Indian Continentaf margin Continentaf Indian western in structure McarofaunaCcommunity ______Occurrence percentage of mean biomass size-spectra for the the for size-spectra biomass mean of percentage Occurrence 0 50 00 2000 1000 500 300 ___ iecass C^m) classes Size ______Chapter

66 | - 2 the study area; a: shelf; b: slope; c: basin. c: slope; b: shelf; a: area; study the Figure 2.6. 2.6. Figure benthic community structure t n Indian Ocean a e c O n a i d n I in y t i e n e g o r e t e h t a t i b a h e h t to e r u t c u r t s y t i n u m m o c c i h t n e b f o e s n o p s e R

V D epths (m) ______, ______MearofaunaCcommunity structure in western Indian ContinentaCmargin Indian western in structure MearofaunaCcommunity

80 90 100 McarofaunaCcommunity structure in western Indian ContinentaCmargin

______Chanter - 2

2556 - 2001 2546 - :------1005 1001 - 1524 - 2443 - 1633 - 2004 - 1247 3150 - 2368 - 2150 ■ tn 3001 J= 600 - t l 2215

H------1------i------1------1 100 80 60 40 20 0 Similarity

Figure 2.7. Cluster and nMDS based on of average macrofaunal density along the study area.

'Response of bent flic com m unity structure to the habitat heterogeneity in Indian Ocean 68 | MearofaunaCcommunity structure in western Indian ContinentaCmargin

______Chapter - 2

[a]

LDJ

Figure 2.8. Distribution o f macrofaunal diversity ([a] Margalef s index d and [b] Shannon-Wiener index H ’) along the western Indian continental margin.

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 69 | McarofaunaC community structure in western Indian Continental margin

______Chapter - 2

■ BMX ■ BSX ■ CDJ ■ CMJ □ CMS □ FDP ■ FST ■ SDF ■ SDT □ SMJ ■ SMT □ SMX □ SST

0 HI 20 30 40 50 60 TO 80 00 100 Feeding types compositon (%)

Figure 2.9. Distribution of Polychaete macrofaunal feeding types along the western continental margin (shelf, slope and basin waters).

Figure 2.10. Photograph of anterior part of Paraprionospio pinnata with well-developed branchia observed in upper the slope OMZ.

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 70 | a

Plate 2.1. Sample analysis during the study in western Indian continental margin

a: ORVSagar Kanya; b: handling the CO2 Culometer analyzer for analyzing inorganic carbon; c: handling the Malvern Laser Analyzer for sediment particle size determination; d analyzing the individual biomass of macrofauna.

‘ Plate 2.2. Some dominant macrofauna along the western Indian continental margin.

a:Aricedea sp.l; b: Cirratulidae sp.2; c: Cossura sp.l; d: Mediomastus sp.; e: Paraprionospiopinnata; f: Syllis sp.; g: shelf water Tanaidacea sp.l; h: deep water (basin) Fanaidacea sp.5. Chapter 3 Community structure and small-scale spatial pattern of deep-sea macrofauna In Central Indian Ocean Basin (CIOB) SpatiaCdistribution of deep-sea macrofauna in CIO8 Chapter - 3

3.1 Introduction

Deep-sea exploration and searching for life below 300 m has begun a little over 150 year ago (Forbes 1844). The deep-sea is considered from about 200 m depth, at the shelf break, where a clear change of fauna from shallow to deep water is observed (Thistle 2003). The water deeper than 200 m occupy the largest ecosystem on this planet with volume of 1368><106 km3 and covering an area of 360 million km2 which is equivalent to about 50% of the earth surface and have an average depth of 3800 m. In 1918, Sir John Ross collected the first deep-sea species ophiuroid Gorgonocephalus caputmedusae Linnaeus, 1758 and Astrophyton linckii, Muller and Troschel, 1842 at 1600 m depth in the Northwest Passage (Menzies et al. 1973), while the evidence of deep-sea faunal richness accumulated only from 1850. The deep-sea floor contains a broad array of habitats such as sediment- covered slopes and plains, rocky mid-ocean ridges and seamounts, and island like chemoautotrophic communities ranging from hydrothermal vents to whale falls. Communities in many of these habitats are likely to be very susceptible to anthropogenic disturbance due to low rates of productivity, growth, colonization, and delicate habitat structure. In fact, the benthic ecosystem of the abyssal depth is a desert deprived of local primary production and is considered as food limited environment (Smith et al. 2008; Sherman and Smith 2009). Consequently the organisms living in abyssal habitats have to depend on supply of particulate organic matter (POM) from the surface waters (Radziejewska 2002). Deep sea benthic macrofauna is described as highly diverse and abundant (Gage and Tyler 1991; Borowski and Thiel 1998; Glover and Smith 2003; Ingole 2003; Ingole et al. 2005; Pavithran ef al. 2007) and majority are considered to be deposit feeders (surface or subsurface deposit feeders or

'Response o f benthic com munity structure to the habitat heterogeneity in Indian Ocean 7111> a g « SpatiaCdistribution of cCeep-sea macrofauna in CIO'S Chapter - 3

generalists) as they depends primarily on the surface primary production (Ingole et al. 1992; 1999; Pavithran et al. 2009). Even though, carnivore predators, scavengers or suspension feeders are present in the deep sea, however at very low abundance (Gage and Tyler 1991). It has been suggested that, the supply of organic material to the abyssal plains of the deep Indian Ocean results from deep-water circulation transporting organic matter from the shelf and slope to abyssal depths (Parulekar et al. 1982; Ingole 2003; Ingole et al. 2010).

Large deposits of polymetallic nodules have been found to occur in the abyss of all the three oceans. Since the nodules occur on 70% of the deep sea floor, it makes the nodule-associated benthic fauna geographically widespread and potentially important in community interaction (Mullineaux 1987). North Pacific and Central Indian Ocean Basin have recorded higher commercial grade nodule deposits (Glasby 1977; Mukhopadhyay et al. 2002; Prasad 2007), with better potential of commercial mining in near future. Compared to the Pacific and Atlantic Ocean, the Central Indian Ocean has low abundance of macro fauna (Veillette et al. 2007; Ingole 2003; Ingole and Koslow 2005; Pavitran et al. 2009) but perhaps has higher faunal diversity (Pavitran et al. 2007; Ingole 2010). Further, the potential higher diversity of benthic biota associated with CIOB ferromanganese nodules provides challenging and scientifically interesting deep-sea environment for researcher. Consequently, a robust environmental baseline data needs to be collected before venturing to any commercial human interference in the deep-sea habitat.

Objectives Considering the fact that Indian Ocean is poorly studied in terms of deep sea benthic biology, the present study was undertaken in the CIOB and aimed to: 1. Study the spatial distribution of macrofaunal abundance, standing

stock 2. Investigate the relationship between community and environmental parameters

'Response o f Benthic community structure to the BaBitat heterogeneity in Indian Ocean 721 P a g c SyatiaC distribution of cfeep-sea macrofauna in CIO'S Chapter - 3

3.2 Materials and Methods

The sediment samples for benthic macrofauna were collected during the deep sea cruise of R. V. Akademic Boris Petrov (Cruise no. ABP 38). Sampling was done at 3 stations with 2-6 replicates of box core in the CIOB between 12°20' to 13°00' S latitudes and 74° 18' to 75°30' E longitudes in the water depth of 5040 to 5220 m (Figure 3.1). A modified USNEL spade box corer of 50 x 50 x 50 cm dimension (sampling area of 0.25 m2) was used for sediment sampling (Plate 3.1.a). Maximum core depth of 39 cm was obtained by the box corer operated at station IVBC 18C. Out of the 14 box core operations, 8 were successful with partial sediments and nodules. Six sediment cores were recovered successfully from IVBC 18, while only two core operations were successful at the IVBC 19 and one at IVBC 20. Details of the samples are provided in Table 3.1. All the nodules were carefully removed from the sediment surface, photographed and preserved individually in 5% neutralized formalin-rose Bengal solution. Two, three or four sub-core (each 10 cm diam) drops were made for macrofaunal sampling at each box core (Plate 3.1 .b) and sectioned at 2 cm interval up to 10 cm and the remaining core was sectioned at 5 cm interval using a locally developed sediment core cutter. This has been the standard sediment sub-sampling interval maintained during the entire MPN-EIA cruises (Ingole et al; 1999; 2000; 2001; 2005; Pavitran et al., 2007; 2009). The water overlying the box core and sub-core sediment samples were sieved through 300 pm mesh screen and then fixed and preserved using 5% neutral formalin-Rose Bengal mixture.

In the laboratory, all the nodule samples were carefully examined for sessile fauna and then washed on 300pm sieve. The material was vigilantly scrutinized under stereo-microscope. All the nodule and sediment fauna were sorted and mounted on temporary glass slide, counted and identified up to the lowest possible taxonomic level.

'"Response of Bent die community structure to the BaBitat heterogeneity in Indian Ocean 73 | F a u Spatialdistribution of deep-sea macrofauna in CIO'S Chapter - 3

Statistical analyses The data were subjected to univariate analyses to study the benthic community structure using M argalefs index (Margalef 1968) for species richness (d), Pielou’s index (Pielou 1966) for species evenness (J ’), and the Shannon-Wiener index (Shannon & Weaver 1963) for species diversity (//'by using loge). The significance of the regions outlined a priori was tested with multivariate cluster analysis and the organisms that contributed most to the observed differences among groups were found by means of SIMPER (similarity percentage) using PRIMER 6 (Clarke & Warwick 1994). Pearson’s correlation between macrofaunal diversity indices and environmental variables was tested using STAT1STICA 6.

3.3 Results

Environmental parameters (Table 3.1) Homogenous clayey silt sediment type was observed along the study area. Low concentrations of sediment Chl-a were observed throughout the study area. Sediment Chl-a ranged from 0.03 to 0.18 pg/g with both higher and lower value were recorded at non-nodule area IVBC 19C and IVBC 20 respectively. Similar to Chl-a value for sediment Corg was also recorded low throughout the study sites. Sediment Corg value ranged from 0.02% to 0.81%. The higher Corg value recorded at IVBC18E while lower value showed at IVBC 20.

Macrofaunal abundance: Population density, biomass and composition

A total of 33 macrofaunal taxa belonging to 11 major groups were identified from the study area located in CIOB (Table 3.2). The average density of three stations (total nine box core among three stations) varied between 127.77 and 477.27 ind m'2 (mean 258.78 ± 68.12 SE) (Figure 3.2). Tanaidacea,

"Response o f Bent flic community structure to tfie RaHitat Heterogeneity in Indian Ocean 74 | v •< <• SpatiaC distribution of deep-sea macrofauna in CIO'S Chapter - 3

Polychaeta, Amphipoda and Isopoda were the dominant groups. Among all the groups, Tanaidacea (34.9%) was the most dominant followed by Polychaeta (23.9%), Amphipoda (18.3%) and Isopoda (11.3%) (Figure 3.4) (Plate 3.2). The least dominant were Nemertinea, Pycnogonida and Bivalvia, each contributing to 1.5% of the total faunal abundance. Among the polychaetes, the m ost dominant genera was Tharyx sp. and family Cirratulidae contributing to 17% each to the polychaete abundance.

Spatial pattern Station IVBC 18 A total of 10 macro faunal groups were recorded from this station. Among them, Amphipoda (29%) was the most dominant followed by Polychaeta (27.5%) and Tanaidacea (23.5%) and Isopoda (6.7%) (Figure 3.5). Nemertinea, Pycnogonida, Oligochaeta, Penaeidae, Pycnogonidea and Bivalvia were the other taxa contributed to 13.4% of macrofaunal abundances. The dominant among amphipods were Amphipoda sp. 4 and Amphipoda sp. 3 contributed to 19% of the total macrofauna along the nodule site. The average faunal density was 267 ind m'2 (± SD 126) among the box cores sampled from the nodule site. The average biomass value was 5.46 mg m' within this area (Figure 3.3).

Station IVBC 19 and 20 Comparatively less faunal groups were recorded at both the non-nodule sites. Total 2 and 3 groups with dominancy of Tanaidaceans (66% and 58%) were observed at IVBC 20 and IVBC 19, respectively (Figure 3.5). Other groups Isopda, Amphipoda and Minor phyla were also found in these sites. Average faunal density was 148 ind m’2 at IVBC 19 and 381 ind m 2 at IVBC 20. The average biomass values were recorded 72.33 and 4.24 mg m at IVBC 19 and IVBC 20 respectively (Figure 3.3).

'Response o f benthic com m unity structure to the habitat heterogeneity in Indian Ocean 7 5 11* a g <• SpatiaC distribution o f deep-sea macrofauna in CI0 3 Chapter - 3

Cluster analysis Cluster analysis based on faunal abundances from box core sample showed distinct pattern between the sites. Two groups were formed showing 15% similarity in the cluster analysis. Group A was restricted within the box cores collected from IVBC 18. This was because of Amphipoda sp. 4 and Tanaidacea sp. 4 contributing to 68% of similarity (Figure 3.6). TheGroup B was consisted of IVBC 19 stations and Tanaidacea sp. 2 was the only taxa recorded (100% similarity).

Species Diversity The data on the species diversity is presented in Figure 3.7. It shows higher Shannon-Wiener diversity index (H ’) at station IVBC 18 (1.84) compared to station IVBC 19 (1.24). Similarly, the Marglef s species richness (d) was also higher at IVBC 18 (1.06) than in IVBC 19 (0.49). However, Pielou’s index (T) for evenness was found to be marginally higher at IVBC 19 (1.00) compared to IVBC 18 (0.97). The values for H\ d and J at single box core station IVBC 20 were recorded 1.09, 0.33 and 1.00 respectively.

Feeding types Deposit feeding habits were mostly dominated in the study area. Further carnivore and filter feeding habits fauna were also present in the macrobenthic composition.

Correlation of biotic and abiotic parameters The biotic and abiotic parameters did not show any significant relationship, except for the negative relation between sand and Margalef s index (d) and Shannon-Wiener diversity index (//’)■

Response o f Benthic community structure to the habitat heterogeneity in Indian Ocean 7 6 1 lJ a » <; SpatiaC distribution of deep-sea macrofauna in CW B Chapter - 3

3.4. Discussions The macrofaunal composition was dominated by Amphipoda, Polychaeta and Tanaidacea with mean density 127.77 to 477.27 ind.m"2. Parulekar et al. (1992) studied the benthos of the western and central Indian Ocean and reported a mean macrofaunal density of 105 ind.m'2 and 92 ind.m"2 in water depths of 5000-5499 m and 5500-5999 m respectively. Further Ingole (2003) reported an average macrofaunal density of 376 ind.m'2 from 56 stations in the depth range of 1254-6005 m. This was mainly due to the inclusion of some shallower stations from the Exclusive Economic Zone (EEZ) of Mauritius and Seychelles. Pavithran (2007) reported the lowest (30 - 44 ind.m'2) macrofaunal density from Central Indian Basin. However, the density reported in this study was the highest from any past report. Compare to past studies higher values of sediment Corg was observed in the present study. As sediment Corg considered as food for benthic macrofauna, which could be reason for high abundance of in the present study. Further, the density of sediment macrofauna observed among the three stations was much higher in the present study compared to the earlier reports which perhaps was due to the difference in sampling technique. The number of replicates used in the present study is comparatively higher compared to all the previous studies from the CIOB region. The Amphipoda, Polychaeta and Tanaidacea were the dominant groups among the macrofaunal communities in the CIOB. The present study therefore corroborates earlier presupposition that crustaceans (Tanaids, Amphipods and Isopods) and polychaetes dominate the soft bottom deep sea sediments macrofaunal community (Ingole et al. 2005b; Galeron et al. 2009; Pavitran et al. 2009). The deposit feeders such as Tanaidacea sp.4, Tharyx sp. and Cirratulidae dominated the macrofaunal community. Deep sea macrobenthos are known represented by filter feeders, deposit feeders or predator (predating, e.g. on meiofauna), but the majority of them are deposit feeders (Sanders 1958). According to numerous benthic reports, the structure o f macrofauna

Response of Bent flic community structure to the habitat heterogeneity in Indian Ocean 7 7 1 P >t ;; SyatiaC distribution o f deep-sea m acrofauna in CIO'B Chapter - 3

depends on the feeding modes of the various species present, which in turn depend on the quality o f available food (Dauwe et al. 1998). Fresh organic matter will result in dominance of suspension feeders while increase in refractory organic matter will enhance the dominance of the deposit feeders. The labile organic matter flux from the overlying waters and conversion of refractory organic matter to labile form by bacteria is considered to be the main source of food for deep sea macrobenthic community (Richardson and Young 1987; Raghukumar et al. 2001; Pavitran et al. 2009). The nature and variability of the organic matter supplied to the deep-sea influence the structure and function of the macrofaunal communities (Grassle and Mose- Porteous 1987). The carnivorous from were equally dominated and were represented by Glycera sp. Glycinde sp., Goniadidae sp. and Onuphis sp. Fauchald and Jumars (1979) suggested that bathyal and abyssal glycerids can also use deposit mode of feeding and hence are capable to adapt to less productive deep sea environment. Earlier studies from CIOB also showed that, bathyal and abyssal glycerids can use both modes (Pavitran et al. 2009) and hence could adapt to the less productive CIOB for their survival. Tanaidaceans which are generally the deposit feeders were well represented in the deep sea macro fauna (Dojiri and Seig 1997) of CIOB (Pavithran et al. 2007). Among the crustaceans, the Isopoda and Amphipods area also particularly abundant and well represented in deep sea sediment (Borowski and Thiel 1998; Brandt et al. 2007). Further, Pavitran et al. (2009) reported higher values of sedimentary proteins compared to the carbohydrates in the CIOB sediment. Higher protein to carbohydrate ratio indicates the presence of fresh flux (Danovaro et al. 1993) and appears to be the most probable reason for the relative abundance of surface deposit feeding fauna in the CIOB (Danovaro et al. 1993). Thus, availability of sedimentary proteins is an important factor regulating the abundance of deep sea benthic consumers. In the present study, there was no relationship found between biotic and abiotic parameters except sand and species diversity. Sand showed the negative relation with species diversity which due to the study area located in

:Response of benthic community structure to the hahitat heterogeneity in Indian Ocean 781 r a a t SpatiaCdistribution o f deep-sea rnacrofauna in CIO'B Chapter - 3

the abyssal floor, basically in calye silt texture. Previous study from CIOB also found the similar texture and negative relation between sandy texture and faunal diversity (Pavithran 2007).

J P ,t "Response of Benthic community structure to the BaBitat heterogeneity in Indian Ocean 79 It * Spatialdistribution of deep-sea macrofauna in CIO'S Cflap ter - 3

Table.3.1. Details of sampling locations and environmental parameters along the study area Station Sam pling Sea bed touch Position of S u b W a te r C lay S ilt San d C h i a oc D ate Number b o x core co re d e p th (P g/g) (%)

Lat (°S) Long (°E) (m)

IVBC 21-9-09 12° 57.679 74° 18.520 4 5041 33.45 55.35 11.2 0.050 0.034 18A IVBC 21-9-09 12°58.842 74° 29.693 5 5164 35.71 54.25 10.04 0.073 0.070 18B IVBC 22-9-09 12v 59.210 74° 26.847 3 5220 35.76 53.84 10.4 0.089 0.054 I8C IVBC 22-9-09 12° 50.934 74° 29.648 3 5164 34.38 54.56 11.06 0.093 0.330 18D IVBC 23-9-09 12° 59.133 74° 28.748 4 5148 29.08 55.32 10.08 0.120 0.810 18E IVBC 23-9-09 12° 59.132 74°29.77 4 5165 32.77 56.21 11.02 0.173 0.721 18F IVBC 17-9-09 13° 00.076 75°30.015 3 5122 26.44 57.97 15.59 0.185 0.703 19C IVBC 18-9-09 13° 00.432 75° 30.260 3 5096 25.38 59.27 15.35 0.083 0.055 I9E IVBC 20 19-9-09 12° 01.044 75°30.614 1 5277 29.08 55.32 15.6 0.034 0.024

Table 3.2. Macrofaunal taxonomic details along the study area

T axa IVBC IVBC IVBC IVBC IVBC IVBC IVBC IVBC IVBC 1 8 E 18F 18B 1 8 C 18D 18A 19C 19F 20 A ricidae sp 0 32 0 0 0 0 0 0 0

CirratuIIidae 3 2 0 0 0 42 0 0 0 0

G lycera sp 0 0 2 5 0 0 0 0 0 0

G lycin idae sp 0 32 0 0 0 0 0 0 0

G on iada sp 0 32 0 0 0 0 0 0 0

H esione sp 0 0 0 0 42 0 0 0 0

O nuphis sp 0 0 0 0 42 0 0 0 0

Tharyx sp 0 32 0 0 42 0 0 0 0

Unidentified 0 127 76 0 0 0 0 0 0 Poychaeta B ivalvia 0 32 0 0 0 0 0 0 0

Amphipoda sp.l 0 0 0 4 2 0 0 0 0 0

Amphipoda sp.2 0 0 0 4 2 0 0 0 0 0

Amphipoda sp.3 0 0 0 0 0 0 42 0 0

Amphipoda sp.4 6 4 32 25 4 2 42 32 0 0 0

“Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 8 0 11' SpatiaC distribution of deep-sea macrofauna in CIOB Chapter - 3

"ToTiphipoda sp.5 0 32 0 0 0 32 0 0 0

Harpacticoid 32 0 25 0 0 0 0 0 0

Isopoda sp. 1 0 0 0 0 0 0 0 4 2 0

Isopoda sp.2 3 2 0 0 0 0 0 0 0 0

Isopoda sp.3 32 0 0 0 0 32 0 0 0

Isopoda sp.4 0 0 0 0 0 0 0 0 127

M inor p h y la 0 0 0 0 0 0 0 4 2 0

N em ertinia 32 0 0 0 0 0 0 0 0

Oligochaete 0 0 25 0 0 0 0 0 0

Peneaidae 0 0 0 4 2 0 0 0 0 0

Pycnogonida 0 3 2 0 0 0 0 0 0 0

Tanaidacea sp.l 0 3 2 0 0 0 32 0 0 0

Tanaidacea sp.2 0 6 4 0 0 0 32 4 2 4 2 0

Tanaidacea sp.3 6 4 0 0 0 4 2 0 0 4 2 0

Tanaidacea sp.4 3 2 0 25 0 4 2 0 0 0 0

Tanaidacea sp.5 0 0 25 0 0 0 0 0 0

Tanaidacea sp.6 0 0 0 0 0 0 4 2 0 0

Tanaidacea sp.7 0 0 0 0 0 0 0 0 127

Tanaidacea sp.8 0 0 0 0 0 0 0 0 127

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 8 1 1 f it •' > SpatiaCdistribution of deep-sea macrofauna in CIO'B Chapter - 3

® Study area

Figure 3.1. Bathymetric map of the sampling locations at Central Indian Ocean Basin

'Response of benthic community struc ture to the habitat heterogeneity in Indian Ocean 82 | SpatiaC dlstnBu t ton of deep-sea macrofauna in CIOS Chapter - 3

800 ■

700 ■

IYBC-18 IYBC-18 IVBC-18 1YBC-18 IVB C -18 1YBC-18 IVBC-19 IYBC-19 IVBC - 20 A B C D E F C E Stations

Figure 3.2. Distribution of macrofaunal density throughout the study area

18 -

IYBC-18 IVBC-18 IVBC-18 IYBC-18 IYBC-18 IVBC-18 IVBC-19 IVBC-19 IVBC - 20 ABCDEFCE Stations

Figure 3.3. Station wise macrofaunal biomass along the CIOB

Kesjeonse of Benthic community structure to tie habitat heterogeneity in Indian Ocean 8 3 1 epne fBnhc omnt tutr t te aia htrgniyi nin Ocean Indian in heterogeneity habitat the to structure community Benthic of Response Macrofaunal composition (%) SpatiaCdistribution o f deep-sea m a cro fa u n a in in a n u fa cro a m deep-sea f o SpatiaCdistribution Figure 3.4. Macrofaunal group composition along the CIOB area CIOB the along composition group Macrofaunal 3.4. Figure Figure 3.5. Box core wise macrofaunal composition in CIOB in composition macrofaunal wise core Box 3.5. Figure IVBC-18 IVBC-18 IV B C -]8 [VBC- 18IV B C - 18IVB C - 18 IVBC-19 IV B C -19 IVBC - IVBC -19 C B IV IVBC-19 18 - C 18IVB - C B 18IV [VBC- -]8 C B IV IVBC-18 IVBC-18 ABCDE □ □ Polvchaeta DNemertinia □ Tanaidacea Nemertinea □ □ Pvcnogonida O Bivalvia phyla □ Minor Stations □ □ Amohinoda □ Isopoda □ Prawn 0 2 E C F CIO'B □ □ Ilarpacticoid □ Oligochaeta Cbapter - 3 -Cbapter 84 | 84 epne jBnhc omnt tutr t te aia htrgniyi nin Ocean Indian in heterogeneity BaBitat the to structure community Benthic oj Response SpatiaCdistributionCIO'S in deep-sea of macrofauna

Figure Figure Diversity value similarity

4.1 Introduction

O n land, mountains and ridge topography are known to increase diversity by offering a multitude of habitat types over small spatial scales and by isolating populations geographically (Flieshman et al., 2000). The exploration of the fauna associated with seamounts, underwater mountains of mostly volcanic origin, began over 50 years ago, after their initial discovery in the 1940s (Hubbs, 1959). Originally, only structures of at least 1,000 m in height were included in the term seamount, but today the smallest topographic features termed seamount are merely 50-100 m in height (Wessel et ah, 2010). Some studies have suggested that seamounts evolutionarily and ecologically ‘function as island groups’ (Richer de Forge et ah, 2000), and potentially show a high degree o f endemism. However, although different seamounts have been shown to harbor different and species rich faunas, observed endemism may be an artifact of under sampling (McClain, 2007; Clark et ah, 2010). Few large studies that compare data from a wide range of habitats on seamounts and non-seamount areas have been conducted so far. For brittle stars, an abundant benthic group, O’Hara (2007) found no difference in species richness and rates of endemism between seamounts and non-seamount areas in the Pacific Ocean. He found that, while seamounts vary in their faunal composition, in species richness and endemism, probably due to differences in their environment, as well as their geological and biological history, the same is true for the continental slope. The marine fauna in general is extremely under sampled, with an estimated 70-80% of marine species remaining to be discovered (Costello et ah, 2010). Thus, claims of endemism should be made

Response of Benthic community structure to the haBitat het erogeneity in Indian Ocean 8 6 1 P ;i » Megafauna fro m JAncCaman 'Back-arc Basin vncCucCing seam ount Chapter - 4

with great caution, but the species rich environments on seamounts offer an opportunity to sample and study rare species with wide distributions. Since seamount summits are found at shallower depths than the surrounding bathyal sea floor, they are more accessible for research. Seamounts function as hotspots for pelagic organisms, mainly fish, which has lead to overexploitation (Pitcher et al., 2010). The benthic communities, which attract these fish, and the interactions between pelagic and benthic organisms, are little understood. An increase in knowledge on seamount ecology is thus vital for the management of a sustainable fishery and the protection of these vulnerable habitats. Due to volcanic and hydrothermal processes, seamounts build up metal deposits that are potentially interesting for high-technology industries (Hein et al., 2010). Large scale mining on seamounts may have severe consequences for the ecology of a whole region. Documentation of the faunal communities living on these seamounts, and the study of the biological processes controlling them are therefore essential for conservation.

Biological data are available for a small percentage of the -12,000 known seamounts (Wessel et al., 2010), mainly from the Atlantic and Pacific Oceans. Of the Indian Ocean seamounts, 15 have been explored biologically, but only four are well documented with regard to benthic biology, form the others single records are known (Stocks, 2009). Particularly the seamounts of the Andaman Sea have not been explored before and are one of the geographic gaps that need to be filled, as recommended by Clark et al. (2010). In the present study we aim to explore the megafaunal community structure of the Andaman Sea seamounts using a quantitative approach. Seamounts differ widely in environmental conditions and habitat properties, which is reflected in the observed differences in species richness and diversity (McClain, 2007; Clark et al., 2010; O’Hara, 2007; O'Hara and Tittenor, 2010). Among the important environmental factors, temperature is correlated to

Response of Bent Hie community structure to the haBitat heterogeneity in Indian Ocean 87 | <> a « <■ Megafauna from JAn dam an “Back-arc “Basin incCucCing seam ount Chapter - 4 species richness, but to a lesser extent also depth, current velocity and other factors may affect the fauna on seamounts (O’Hara and Tittenor, 2010). McClain (2007) suggested that hard substrate seamounts have received considerably more attention than soft bottom ones, which may result in biased datasets. It is well known that hard bottoms promote the development of communities associated with sessile organisms, such as corals and sponges, whereas soft bottoms are typically inhabited by more or less motile fauna.

Objective Based on geomorphological features, geology and bathymetric gradient, the aim of the present work is to investigate how substratum types and shape affect the community structure within and between the seamounts.

Hypothesis

Based on the previous literature, the testing hypothesis is that hard substratum types such as boulders and cobbles will be species richer than fine sediment types on Andaman seamounts along with the basin region.

’Response of Benthic comm unity stvuctuve to the hdBitcit hetevogeneity in IncCidn Ocecin 88 j ^ a & *.■ Megafauna from ^Andaman 'Back-arc Basin inc CucCing seamount Chapter - 4

4.2 Study area The volcanic-arc trench system of the Andaman Sea represents a submarine extreme boundary of the Indian plate in the northern Indian Ocean (Figure 4.1). The plate margins have several unique geophysical provinces, which include the arc-volcanoes, seamounts, deep sea valley, and the back-arc basin. The water depth varies from a few hundreds of meters to more than 3000 m, thus marking different ecological set-ups in the deep sea.

4.3 Materials and Methods The Andaman Back-arc Basin (ABB) is an active marginal basin in the northeastern Indian Ocean, marking the eastern boundary of the Indian plate, sub-ducting beneath the Southeast Asian plate. Convergence of the plates leads to formation of several geomorphological features, like the Andaman- Nicobar island-arc, the Andaman back-arc spreading center, the seamount complex, and the back-arc basin (KameshRaju et al., 2004), (KameshRaju et al., 2007) (Figure 4.1). Recently a submarine volcano (crater seamount-CSM) with crater (160 m deep) on its summit was discovered in the Nicobar Earthquake Swarm area (07°55’N, 94°02’E). This seamount is conical in shape and has a steep slope, similar to aerial stratovolcanoes in the Andaman- Sumatra region. The Andaman spreading center is a deep-sited (maximum depth > 4000m) SW-NE-trending, spreading ridge-like feature that bisects the basin (KameshRaju et al., 2004). Two underwater video surveys and sampling (TVG-9 and TVG-10) were carried out on the CSM off Nicobar Island. The flank of the CSM was surveyed during TVG-9 (average depth 594 m), while TVG-10 (avg. depth 434 m) was deployed inside the summit crater to investigate the crater-floor. Another seamount (SM2 at 10°N, 94°E, (KameshRaju et al., 2004), which is not a volcano but flat topped and part of the arc-parallel seamounts chain in the Andaman Sea, was explored with two more TVG operations and samplings. TVG-12 was deployed on the summit

Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 8 9 11' ,t - t Megafauna from Andaman 'Back-arc 'Basin incCuding seamount Chapter - 4

(depth 1336 m) of the SM2, while TVG-11 (avg. 1357 m) was operated on the flank of this seamount. TVG-13 was deployed along the valley floor (avg. depth 2897 m) while TVG-14 was on the off-axis basin (avg. depth 1791 m) of the Andaman spreading center.

Data collection

Collection of megafaunal (video) data from six transects in the ABB were undertaken during November 2007 with the scientific research vessel RV Sonne. The details of sampling locations and depth are given in Table 4.1. Video sampling transects were selected using the EM 120 multi-beam system data. We used the global seafloor topography from satellite altimetry and ship depth soundings data (Smith and Sandwel 1997) for seamount mapping. Seamount benthic communities were sampled using video transects collected with the Television guided Gripper (TVG) system (0.6 m3) (see Chapter 5, Plate 5.1). It was operated from the starboard side of the vessel. The system integrated 4 X ROS QL 3000 spotlight, 1XDSPLMSC 200 color, and 1XOSPREY OE 1390 black and white digital video telemetry systems, which provided a real time video link to the surface for maximum quality, digital through a fiber optical LWL cable. These video images were collected on DVD for further examination. The minimum length of the TVG tow was 389 m while the maximum was up to 1664 m. The vessel speed was approximately 0.7 knots during the TVG operations. The drop frame was towed in the water column between 1 and 3.5 m (dependent on bottom substratum types) above the seabed. The width of coverage of a single frame was approximately 2.5 m, but varied with distance from the bottom and angle of tilt. This width of the video has been used to calculate the total area covered by TVG during each transect sampling. All megafauna were identified to lowest possible taxon during the underwater video observation or later by the taxonomists (see acknowledgement).

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 90 | !> -i s v Megafauna from Andaman 'Back-arc ‘Basin incCucCing seamount Chapter - 4

Although every effort was made to identify the fauna to the lowest possible taxon, assignment to species was not always possible. For organisms that were morphologically distinct, but not sampled, and therefore not identified to species level, we used the higher taxon name with respect to different ‘Tag’ number such as Octocorallia sp.l, Octocorallia sp.2 or Actiniaria sp.l etc. Several groups such as spider crabs, lithodid crabs, galatheidae, corals, sponges, feather stars, and sea stars, could not be confidently identified to species level from the video images and were grouped into larger categories. Other species were confidently identified to genus or higher taxon level. However, we collected some specimens using the hydraulic arms of the TVG for proper taxonomic identification. The locations were selected based on the video image and the TVG can be closed from onboard by transmitting a command to the arms. Samples were collected from the end point of each TVG location. Sessile fauna such as sponges and corals were carefully brushed from the rocks. Preliminarily, all collected fauna was preserved in 30% ethanol, but subsequently transferred to 70% ethanol. We also collected some bird nest sponges from the flank of the SM2 seamount, separated them carefully from the sediment and immediately preserved them in 70% ethanol. In the laboratory, all samples were washed carefully and the entire faunal community associated with sponge spicules was sorted out and preserved in70% ethanol for further identification.

Image analysis Videos were reviewed and megafaunal communities were identified and quantified. Bottom substratum types were determined by estimating the percentage of boulder, cobble, or fine sediment present, following the description of Hoff and Stevens (2005). The substratum types were classified by size, approximating the Wentworth grade scale (Holme and McIntyre 1984), with boulders being defined as large rocks (>0.2 m diameter) to complete bedrock; cobble was rocks of 0.2-0.5 m diameter, and fines a

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 9 1 1 i‘ i - <- Megafauna from Andaman 'Back-arc Basin incfuding seamount Chapter - 4

bottom type of similarly sized gravel, sand and finer sediments of <0.05 m diameter. These groups were attributed an alphabetic code between #1 and #14 on overall composition of the bottom types (Table 2). We defined each habitat patch as a video observation of about 5 minutes duration, which covered 108 m length. We used these habitat patches to calculate and quantify the substrate types and megafaunal abundances of each transect. The area of each habitat patch was determined by multiplying the transect width (average 2.5 m) with the length of the habitat patch. Then we compared the community composition within and between the seamounts.

Categories of motility were assigned to all observed taxa and analyzed to determine the functional role of dominant members of the seamount communities and the basin area. Organism motility was classified as sessile (e.g. sponges, corals), mobile (e.g. arthropods, chordates, ophiuroids, echinoids and holothuroids) and functional sessile (e.g. crinoids).

Statistical analysis Only those species that could be confidently identified from up to 3 m off the bottom were included in the analysis. The data were subjected to univariate analyses to study the benthic community structure, using Margalefs index (Margalef 1968) for species richness (d), Pielou’s index (Pielou 1966) for species evenness (J’), and the Shannon-Wiener index (Shannon and Weaver 1963) for species diversity (H’ by using loge). To investigate how similarity among assemblages changes with the substratum types and bathymetric gradients in the ABB, several multivariate analyses were conducted using routines in PRIMER v6 (Clarke 2006). Following the general recommendations of Clarke and Warwick (1994), the Bray-Curtis similarity measure was employed to assess multivariate similarity and dissimilarity between transects based on both presence/absence and log- transformed faunal abundance data. The significance of transects outlined a

•Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 92 | (' :> a Megafauna from Andaman 'Back-arc Basin incCuding seamount Chapter - 4

priori was tested with multivariate analysis (non-metric Multi-Dimensional Scaling (nMDS)) and the organisms which most contributed to the observed similarity within and dissimilarity among groups were found by means of SIMPER (similarity percentage). The habitat patches data of each transect were used for the nMDS analyses, using group averages, to explain the difference between transects for substrate types and megafaunal abundances. Using the RELATE test in PRIMER, we tested the Spearman rank correlation between the faunal similarity matrices as faunal abundance and percentage of groups, and model similarity matrix based on three different types of substratum, i.e. that faunal similarities are related to depth differences and substratum types among transects. Linear regression between biotic parameters (diversity indices) and environmental variables was tested using STATISTICA 6.

’Response of Bent Hie community structure to the BaBitat heterogeneity in Indian Ocean 9 3 1 r * <1 Megafauna from Andaman Back-arc ‘Basin incCuding seamount Chapter - 4

4.4 Results

Habitat structure Seamounts Diversity of substrate types was greatest for both seamounts, varying from boulders to fines (Figure 4.2). The boulders varied from smooth basalt spires to jagged uplifted slabs.

CSM Transects located at the CSM had mostly rocky substratum, while both transect, summit and flank were dominated by boulders and cobbles. However, eight unique combinations of physical substrate were observed from a total of 20 habitat patches at the CSM. The highest percentage of boulders (23.3%; code #2) and cobbles (47.8%; code #8) were recorded from the summit and flank of the CSM seamount. A lower percentage of fine sediment was observed at both transects.

SM2 Ten combinations of physical substrate were observed on 13 habitat patches of the transects located on the SM2 (Fig. 2). Fines and cobbles substrates dominated on both summit and flank. A maximum of 41.9% (code #13) and 32.3% (code #14) of fine sediments was observed at flank and summit respectively.

Basin Other transects (off-axial highs and valley floor) located in the back-arc basin, had a fine sediment type of substrates. Particularly, the valley floor had at maximum 93.8% fine sediments.

Response ofhenthic community structure to the habitat heterogeneity in Indian Ocean 94 | ydegafauna from ^Andaman 'Back-arc Basin incCucCing seamount Chapter - 4

Megafaunal community structure A total of 948 individuals from 58 taxa, representing eight phyla, were observed in the collected samples and video images. The taxonomic catalogue is available online as supporting information. Faunal abundances were highest on the seamount area and lower in the basin region (especially in deeper parts). Density counts varied from 7.4 to 345.2 ind. 1000 m'2 (mean 89.9 ± 6.4) along the study area (Figure 4.3). The highest number of taxa (40) and individuals was observed on the flank of the CSM seamount (depth o f 517-671 m). Quantitative video transects at the CSM and SM2 seamounts differed in mean faunal density. Twenty habitat patches from two transects were identified between 373 and 671 m depth at the CSM seamount. These transect varied in length (497 to 1664 m) and width (1.25 to 5.8 m). Faunal density averaged 197.6 ± 14.5 ind. 1000 m'2 (range = 50 to 345.2 ind. 1000 m"2). Thirteen habitat patches from two transects were identified between 1290 and 1424 m at the SM2 seamount. These transect varied in length (389 to 994 m) and width (1.12 to 3.2 m). The faunal density averaged 56.8 ± 2.9 ind. 1000 m'2 (range = 25.9 to 87.7 ind. 1000 m'2).

Assemblage composition and dominant taxa The overall megafauna was dominated by sponges (30.9%), but cnidarians (25.3%) and echinoderms (24.9%) were also important components along the study area (Figure 4.4).

Seamounts CSM

The highest abundance (mean 345 ±21.5 ind. 1000 m"2) was observed at the flank of the CSM seamount, at depths between 517 m and 671 m, where the substratum was categorized mostly by cobbles mixed with fine sediments (code #8). Seven groups were found on the CSM seamount, all of them at the

Response of henthic community structure to the habitat heterogeneity in Indian Ocean 95 | f ;i s; v Megafauna from JAncCaman 'Back-arc Basin incCucCing seamount Chapter - 4

flank, while only five groups were represented at the flank. The sessile group porifera (48.6%) was clearly dominant on the flank, while the mobile groups echinoderms (38.4%) and arthropods (22.2) dominated at the summit (Figure 4.4). .Among all the transects, the flank of the CSM exhibited the highest number (13) of cnidarians, although this group contributed to 18.0% of the total megafaunal abundance along the ABB. The hexactinellid sponge Euplectella sp. was well distributed and the most dominant taxon across the entire flank. It contributed with 33.6% to the total megabenthic community at the flank of the CSM, followed by demospongiael (10.5%) and Corallium sp. (3.2%), as the next dominant taxa in this region. Ophiura sp. (16.3%), demospongiae2 (14.8%) were the top ranked taxon at the summit of the CSM. The structure of CSM seamount and their associated megafauna is represented in Figure 4.5.

SM2

The second abundant (87.7 ± 2.6 ind. 1000 m'2) area of the megafaunal community was observed at the flank of the SM2, at depths between 1299 m and 1424 m, where the substratum mainly consisted of fine sediments with cobbles (code #13). Six groups of megafauna were observed on the SM2, the flank exhibited all groups, while only three groups were found at the summit. The sessile group Porifera was dominant at both areas of the SM2, contributing 57.1% and 37.5% at the summit and flank respectively. Further, Arthropoda was the next dominant (25.3%) group at the flank of SM2, although this group was not observed at the summit. Cnidarians were the second dominant group next to the Arthropoda at the summit (28.6%) and flank (20.4%) respectively. The bird-nest sponge Pheronema sp. was the most dominant species on both areas of the seamount SM2 and contributed with 20.6% at the flank and 28.6% at the summit to the megabenthic community. Further, demospongiae3 and Viminella sp. were the next dominant at the flank

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 96 | p o « ,• Megafauna from Andaman Back-arc 'Basin mcCucCing seamount Chapter - 4 of SM2 seamount. Structure of SM2 seamount and its associated megafauna is represented in Figure 4.6.

Basin

Faunal abundances were poor on the basin transects. The observed abundance of megafauna on the transect on the valley floor was 23.1± 2.2 ind. 1000 m'2 at depths between 2876 m and 2917 m, where fine sediments were completely dominant. Among four groups found in the basin area, all were observed on the valley floor, where off-axial highs showed two groups only. Echinoderms (especially holothuroidea5) and cnidarians (especially whip coral Viminella sp) were the dominant groups in the basin area. The most dominant group was the echinoderms (50%) at the off-axial highs, while they constituted 36% at the valley floor transect. The striking feature was that only the sponge Hyalonema sp. was observed on the valley floor located in the Basin area.

Sessile and mobile organisms accounted for most of the observations, while functionally sessile fauna was rare over the entire study area (Figure 4.7). Sessile fauna was the largest component of the community at the SM2 seamount, but the smallest in the basin area

Multivariate (MDS) analysis of substratum types and megafaunal community The MDS plot based on the average percentage of substratum types found two groups with 50% similarity (Figure 4.8). Transects located on the flank of both seamounts formed group 1, because the substratum type cobbles mixed with fine sediments (code #8) contributed the highest similarity percentage (Table 4.3). Similarity of fine sediment types substratum allowed to form another group 2 between the summit of the SM2 and the off-axial highs in the basin area.

•Response of benthic community structure to the habitat heterogeneity in Indian Ocean 97 1!‘ « c Megafauna from Andaman Back-arc Basin incCucCing seamount Chapter - 4

The MDS plot based on the average abundance of megafauna also revealed two distinct groups with 25% similarity (Figure 4.9), each restricted to one of the two seamounts. Transects located on the CSM formed group A, while group B was formed by the SM2 transects. Some echinoderms (e.g., Ophiura sp., ophiuroideal, holothuroideal etc.), asteroideal, actinarial, galatheidae and fishes played a major role in forming group A within the CSM transects (Table 4.4). In contrast, the bird nest-sponge Pheronema sp. and gorgonacea sp.2 were the most important organisms for forming group B on the SM2 seamount. The dissimilarity between the groups showed by the SIMPER analysis is presented in Table 5. Among 57 taxa observed on two seamounts, 46 taxa accounted for about 91% of the dissimilarity between the seamount faunal assemblages.

Diversity indices The highest number of species (S) (41) was observed at the flank of the CSM, while the lowest (2) was recorded in the off-axial highs area (Figure 4.10). Margalefs index (d) o f species richness varied from 0.5 to 6.8, the higher value recorded at the flank of CSM and the lower at the off-axis basin area. Pielou’s index (J’) of evenness varied from 0.8 to 1.0, with both transects on the flank showing lower values than other transects along the study area. Values of FT varied from 0.7 to 1.9 along the study area.

Correlation between substratum types and biotic community parameters Specific faunal groups exhibit varying responses related to substrate composition (Table 4.6). Total abundances (Log x+1 transformation) of the ABB showed a significant positive relationship with cobbles only. Porifera and Cnidaria exhibited the strongest positive relation with cobbles rather than with fines sediment, whereas Echinodermata and Arthropoda showed a significant positive relation only with fine sediments. No animal group showed a significant relation to boulders. The correlation between faunal

'Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 98 H* ;» a v Mego-fluna from JAncCaman 'Back-arc Basin incCuding seamount Chapter - 4

diversity and substratum types was based on Pearson’s correlation analyses (Table 4.7). Megafaunal species richness (S), Margalefs index (d) and Shannon-Wiener index {H ’) were positively correlated with cobbles, while these three diversity parameters were negatively correlated with fine sediments. Again boulder did not play any significant role with relation to faunal diversity parameters. Moreover, substratum types did not show any correlation with motility categories.

4.5 Discussion

Seamounts are vulnerable environments and should be protected from destruction, which requires techniques and methods of documentation that cause as little damage as possible. To this end, most studies use under-water video images to explore the seamount fauna. McArthur et al. (2010) suggested that fauna associated with hard substratum (e.g., cobbles, boulder) is best explored by underwater video or images. Accordingly, we have inventoried the megafauna of Indian Ocean seamounts, using under-water video. The analysis of the video images showed that the volcano CSM consists of a rugged rocky environment made up o f large boulder fields, and various sized cobble on the flank (Figure 4.9). Hard substrata, typical for the deep-sea environment, are common on seamounts and may take the form of rocks or cobbles (Raymore 1982). Seamounts are primarily of volcanic origin, dominated by pillow lavas and basalts, which form boulders or cobbles later (Wright 1994). Accordingly, the CSM which has been reported as a submarine volcano, also presented the largest proportion of hard substrata, formed by boulders and cobbles. Underwater video analysis of substratum types also showed the highest percentage of boulders and lowest percentage of fine sediments at the crater summit of the CSM seamount. Further, this crater

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 99| i> a 2 . Megafauna from JAncCaman ‘Back-arc Basin incCucfing seamount Chapter - 4

summit has been suspected as a mouth of the volcano, which may be the reason for the high percentage of boulders and cobbles on the CSM. Compared to the surrounding areas of fine sediment-covered basin area, there was a marked difference in the abundance of coral and sponges on the seamount. The higher mean faunal density found on the CSM seamount, which has a shallower summit than the SM2 seamount, is likely due to nutrient availability, which increases with depth globally in concert with an exponential decline in faunal abundance and biomass (Rex et al, 2006). In areas of upwelling, sessile suspension feeders, such as corals and sponges and the associated fauna, find suitable conditions on hard bottoms (Hoff and Stevens 2005). Hoff & Stevens (2005) found for the Patton Seamount (Alaska) that suspension feeding communities were most abundant in the upper 1500 m, where it is still possible to take advantage of the photic zone. We observed lower faunal abundance and species diversity for the summit of the CSM seamount that is located just beneath the photic zone, than for the flank. Further, the SM2 also showed the same results as the CSM, with higher abundances and diversity on the flank than on the summit. This may be due to (unknown) differences in current velocities, because filter feeders require relatively fast currents (Clark et al., 2010). The MDS analysis o f faunal abundances did not find any group between seamounts, because of distinctness of the seamount faunal communities. This faunal distinctness between the seamounts was caused by those species which had their highest abundance on the same seamount and contributed some percentage to the dissimilarity (Table 4.5). Some species, such as Euplectella sp., were dominant and found only on the CSM seamount, whereas others, such as Pheronema sp., were dominant and only seen on the SM2. Dense aggregations of the bird-nest sponge are also known to occur at depths of 750- 1300 m on the slope of the Porcupine Seabight in the NE Atlantic Ocean (Rice et al., 1990) and off Morocco (Barthel et al., 1996). Species presence restricted to a specific area is a character o f endemism, although the degree of

Response of Benthic community structure to tfie ficiBitcit heterogeneity in Indian Ocean 100 | Megafauna from Andaman "Back-arc "Basin including seamount Chapter - 4

endemism cannot be ascertained from this study. Further, faunal distinctness between seamounts was also caused by differences in environmental conditions, such as depth and substratum types. During the underwater observation, it was found that faunal abundance changed with changing substratum types. This was confirmed by the MDS analysis, which showed that faunal abundance and substratum types followed the same pattern, and by the RELATE analysis, which showed a significant positive relation (p = 0.001) between abundance and substratum types (Table 4.5). Further, cobbles substratum also showed up in the MDS o f substratum types, with 50% similarity between the flanks of both seamounts. Abundances were also higher on flanks than on summits of both seamounts and in the basin area. These findings support our hypothesis that geomorphology plays an important role for structuring the megafaunal communities in the ABB. During the underwater observation we noticed that categories of motility changed with changing substratum types. However, faunal motility and substratum types did not show any correlation within the study area, probably because of the presence of some sessile categories such as sponges Hyalonema sp., Demospongiae sp. 1 and whip coral Viminella sp., found attached to the hard substratum, as was occasionally observed in the basin transects. A large proportion of the fauna on the ABB seamounts consists of many attached and sessile, as well as mobile suspension feeders (sponges, corals, crinoids, brittle stars and holothuroids). The shallower transect, located at the summit crater, showed a comparatively large component o f mobile Ophiura sp. It was observed that attached and sessile suspension feeders were fewer in the crater area than on the flank of the CSM seamount. This may be caused by to the geomorphological setting, such as the crater formation of the area, possibly creating a weak current flow, thus limiting the effect of the productive upwelling characteristics. Many sessile animals, such as gorgonians and black corals, require hard substrata and strong currents that supply them with food and oxygen, remove waste products and continuously

Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 101 f f A <* t! Megafauna from Andaman 'Back-arc Basin including seamount Chapter - 4

keep the substratum, including the corals, completely clear of sediment (Grigg 1974; 1984). In the deep-sea such types of conditions are observed in very few habitats, seamounts are one of them. The high abundance and diversity of sessile fauna on both seamounts compared to the basin area also support our assumption that the hard substrata of seamount habitats are more favorable for rich megafaunal diversity than fine sediments.

4.6 New insights from the present study The degree of endemism and speciation on the Andaman seamounts is unknown, although new species (e.g., Hyalascus andamanensis Sautya et al., 2010) and new records (e.g., the epibiont Thecacineta calyx Schroder, 1907) have been reported from the CSM. Several of the ophiuroids collected by us are described in Chapter 6.C. Further, the present investigation provides additional knowledge of the seamount fauna as well as the deep-sea biodiversity of the Indian Ocean (Figure 4.11). Records of sponges from the seamounts of the world oceans (Figure 4.12) also confirm the earlier notion that the Indian Ocean is a poorly studied region. Prior to this study, there were only reports on Porifera and Hexactinellida from the Indian Ocean seamounts, while the present study not only added some more records of sponge species (e.g., Pheronema sp.; Figure 4.13) to the global seamount map, but also showed potential for the discovery of new species, if sampled systematically.

4.7 Conservation of Andaman seamounts The present investigation demonstrates the pristine condition of benthic communities on the seamounts, with negligible evidence of human impact. The communities are found in greater abundance and better health than those found in less-optimal habitat, suggesting that seamounts may be a source, rather than a sink, for some species (McClain et al., 2009). Deep-water black corals (antipatharians) have substantial potential as proxy records of historical

'Response o f Bent file com m unity structure to tBe BaBitat Beterogeneity m Indian Ocean 102 | Megafauna from Andaman 'Back-arc Basin incCuding seamount Chapter - 4 oceanographic and biogeochemical changes (Grange and Goldberg 1994). Their long life-span, wide geographic distribution and wider depth range (Grigg 1965) suggest that they may provide environmental information for geographic locations and for periods of time that are not available from other sources. Thus, they can be a potential source for paleoceanographic studies. Our study suggests that the Andaman seamounts are biologically rich, home for many new species, and an optimal habitat for benthic organisms. We suggest that the region should be conserved for future biodiversity research. Conservation of these seamounts is also expected to ensure a survival and supply of ecologically important species that can disperse to depleted areas and replenish them.

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 103 | jiiegufaunafrom Andaman 'Back-arc Basin incCuding seamount Cdapter - 4

^ 4Xvid^observations on seamounts (CSM and SM2) and bathyal sea floor (back-arc basin) in the Andaman Sea. Detail of locations, depths and approximate area covered for each transect conducted by the TVG (television operated video gripper).

Area Station Date Start Start Lat End End Lat Min. Max. Area ID Long (E) (N) Long (E) (N) Depth depth covered (m) (m) (m2) 26/11/2007 94°02.638 07°56.330 94°02.693 07°56.255 373 494 1242.4 jUCSM Summit (TVG-10) Flank 25/11/2007 94°03.139 07°55.924 94°03.026 07°56.036 517 671 4159.3 (TVG-9) ISM2 Summit 27/11/2007 94°00.784 10°00.243 94°00.813 10°00.255 1299 1372 972.3 (TVG-12) 1'------Flank 27/11/2007 93°57.137 09°59.500 93°57.260 09°59.526 1290 1424 2484.8 (TVG-11) Back- Off-axial 30/11/2007 93°51.978 10°33.599 93°52.149 10°33.646 1767 1814 1404.4 arc highs Basin (TVG-14) Valley 30/11/2007 94°09.500 10°27.200 94°09.590 10°27.590 2876 2917 1512.5 floor (TVG-13)

Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 104 1 Megaf %unafrom Andaman "Back-arc Basin incCuding seamount Chapter - 4

Table 4.2. Composition of substratum types used for assigning substrate codes to observed habitats viewed from video images from the TVG in the Andaman Back-arc Basin. % of each substrate type Substrate Boulder Cobble Fines Substrate code classification #1 100 Boulder #2 75 25 Boulder #3 75 25 Boulder #4 50 50 Boulder #5 50 25 25 Boulder #6 25 75 Cobble #7 25 50 25 Cobble #8 75 25 Cobble #9 100 Cobble #10 25 25 50 Fines #11 50 50 Fines #12 25 75 Fines #13 25 75 Fines #14 100 Fines

^ponse of Benthic community structure to the hahitat heterogeneity in Indian Ocean 105 h n f Megaftuna from Andaman 'Back-arc 'Basin incCucCing seamount Chapter - 4

Codes Av. Av. C ontrib% Cum% A bund Sim Group 1 (flanks of #8 36.73 26.06 48.69 48.69 CSM and SM2). Average similarity: 53.52

#11 12.71 11.62 21.71 70.4 #4 9.61 7.88 14.73 85.13 #2 4.49 3.72 6.96 92.09 Group2(SM2 summit #14 26.56 20.8 31.7 31.7 and off-axial highs in basin). Average similarity: 65.63

#10 24.75 18.03 27.47 59.16 #13 22.67 16.92 25.79 84.95 #8 12.83 9.88 15.05 100

Species Av. Av. C ontrib% Cum% A bund Sim Group A Ophiura sp 1.88 3.27 12.5 12.5 (summit and flank of CSM). Average similarity: 26.15 Ophiuroidea sp.l 1.93 3.27 12.5 25 Asteroidea sp. 1 1.61 3.27 12.5 37.5 Holothuroidea sp.2 1.55 3.27 12.5 50 62.5 Actiniaria sp.2 1.55 3.27 12.5

the habitat heterogeneity in Indian Ocean 106 | ‘Response of Benthic com m unity structure to Megafauna from JAndaman Back-arc Basin including seamount Chapter - 4

Galatheidae sp.l 1.71 3.27 12.5 75 Anguilliformes sp.l 1.66 3.27 12.5 87.5 Actinoperygii sp.l 1.55 3.27 12.5 100 Group B Pheronema sp. 2.54 10.82 40.74 40.74 (summit and flank of SM2). Average similarity: 26.56 Gorgonacea sp.2 1.64 7.87 29.63 70.37 Elasmobranchii sp.l 1.55 7.87 29.63 100

the habitat heterogeneity in Indian Ocean 107 | Response of Benthic community structure to Megaf lunafrom JAndaman Hack-arc 'Basin including seamount Chapter - 4

Table 4.5. SIMPER analysis ot average abundance dissimilarity between organism groups A and B on two Andaman Sea seamounts. Average dissimilarity = 91.92. Average abundance (av. abund), average dissimilarity (av. diss), quotient of dissimilarity and standard deviation (diss/SD), contributed percentage (contrib%), cumulative contribution (cum%). Here we presented the faunal contribution percentage for dissimilarity between the groups up to 50%.

Group A Group B Species Av.Abund Av.Abund Av.Diss Diss/SD Contrib% Cum.% Pheronema sp 0.77 2.54 3.91 1.14 4.26 4.26 Ophiuroidae sp.l 1.93 0 3.39 2.35 3.68 7.94 Anguilliformes sp.l 1.66 0 3.31 1.5 3.6 11.55 Galatheidae sp. 1 1.71 0 3.16 1.92 3.44 14.98 Gorgoncea sp.2 0 1.64 3.12 1.74 3.4 18.38 Asteroidae sp. 1 1.61 0 3.05 1.74 3.32 21.7 Holothuroidea sp.2 1.55 0 2.99 1.65 3.25 24.95 Actiniaria sp.2 1.55 0 2.99 1.65 3.25 28.2 Elasmobranchii sp. 1 0 1.55 2.99 1.65 3.25 31.45 Actinopterygii sp.l 1.55 0 2.99 1.65 3.25 34.7 Demospongiae sp.2 1.06 0 2.98 0.81 3.25 37.94 Ophiura sp 1.88 0.77 2.75 0.79 2.99 40.93 Demospongiae sp. 1 1.81 1.06 2.51 1.16 2.73 43.66 Euplectella sp 2.38 0 2.51 0.86 2.73 46.4 Decapoda sp. 1 0.77 0 2.17 0.81 2.36 48.76 Spider crab 0.77 0 2.17 0.81 2.36 51.12 Paragorgiidae sp. 1 0.86 0.77 1.82 0.72 1.99 53.1

Response of Beni flic community structure to tBe BaBitat Beterogeneity in Indian Ocean 108 | Megafauna from Andaman Uadi-arc 'Basin incCudmp, seamount Chapter - 4

Table 4.6. RE LATE analysis between substratum types and biotic parameters in the Andama n Back-arc-Basin (ABB). Bold numbers indicate significant values. Substrate Transformation G roup Rho p-value type______Boulders Log x + 1 ABB total -0.083 0.95 P/A ABB total -0.073 1 Porifera -0.134 1 Echinodermata 0.015 0.34 Cnidaria 0.032 0.281 Arthropoda -0.043 0.71 Chordata -0.039 0.69 Mollusca 0.024 0.29 Sipuncula -0.053 0.602 Cobbles Log x + 1 ABB total 0.394 0.001 P/A ABB total 0.024 0.39 Porifera 0.239 0.002 Echinodermata 0.093 0.062 Cnidaria 0.133 0.001 Arthropoda 0.055 0.151 Chordata 0.024 0.247 Mollusca 0.195 0.031 Sipuncula 0.005 0.476 Fines Log x + 1 ABB total 0.302 0.00001 P/A ABB total 0.017 0.456 Porifera 0.143 0.007 Echinodermata 0.118 0.013 Cnidaria 0.115 0.02 Arthropoda 0.122 0.037 Chordata 0.065 0.116 Mollusca 0.079 0.157 Sipuncula -0.005 0.498

the habitat heterogeneity in Indian Ocean 109 | 'Response of Benthic com m unity structure to Megafauna from Andaman Back-arc Basin incCuding seamount Chapter - 4

Substratum S d J' H’ type Boulder 0.0376, 0.0321, 0.2645, 0.1622, p=.838 p=.087 p=.299 Cobbles 0.6577, 0.4915, 0.1285, 0.4286, p=.000 p=.001 p=.411 p=.004 Fines 0-.6065, -0.4596, -0.2110, -0.4830, p=.001 p=.002 p=.174 p=.001

“Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 1101 Megafauna from Andaman Back-arc Basin incCuding seamount Chapter - 4

meter -4000 -2000 0 2000 Depth

Figure 4.1. Bathymetric map of the Andaman Back-arc Basin including Andaman Back-arc Spreading Centre (ABSC) and locations of the underwater video transects (TVG). All the transects were located in the Back-arc Basin region only. The TVG-9 and TVG-10 were located on the cratered seamount (CSM) off Nicobar Island, TVG-11 and TVG-12 were located on the back-arc spreading ridge segments, while TVG-13 and TVG-14 were located on the rift valley of the basin floor and on the off-axial highs of the back-arc basin.

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 111 | Megafauna from Andam an Hack-arc Vasin incCucfinq seamount Chapter - 4

Figure 4.2. Composition of substratum types of two seamounts and surrounding sea floor in the Andaman Back-arc basin, with transect codes. Please see Table 2 for details of substratum types.

Figure 4.3. Megafaunal abundance along depth for two seamounts and the surrounding deep sea in the Andaman Back-arc basin.

• Ponfera ■ Echinoderm ala » Cm ! ana ■ Arthropods ■ Chordata ■ Mollusca • Slpuncula

Occurrence percentage

Figure 4.4. Megafaunal group composition along the CSM and SM2 seamounts and basin area in the Andaman Sea Back-arc Basin.

"Response of benthic community structure to the habitat heterogeneity in Indian Ocean U2 | Megfaunafram Andaman ■BaOcarc -Basin induing seamount

Figure 4.5. Structure of the CSM seamount (3D model midified from Kattoju et al. 2010) with accurate locations of the TVG-10 at summit and TVG-9 at flank, and the fauna associated with it. Megabenthic communities observed on a crater seamount in the Andaman Sea. a: Holothurid; b: Euplectella sp.; c: Gorgonian; d: Squat lobster - Galatheidae; e: Demospongiae attached to a big rock, onboard sample; f: the squat lobster- Liogalathea laevirostris; g: brittle star- Ophiophyllum sp; h: dense population of megafaunal communities (gorgonians, sponges, sea urchins, brittle stars, galatheids) lived on the big boulders and uplifted slabs; i: dense patches of corals (gorgonians); j: Ophiuroidea laid on the cobbles substratum.

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 113 Megafauna from Andaman 'Back-arc Vasin incCucCing seamount Chapter - 4

Figure 4.6. The SM2 seamount with locations of TVG-12 at summit and TVG-11 at flank, and its associated fauna. a:The bird-nest sponge Pheronema sp; b: Munida sp; c: Pycnogonid; d: Arrow indicating the underwater photograph of bird-nest sponge; e; Black coral attached to the hard substratum.

70 a Sessile ■ F.S ® Mobile

Figure 4.7. Occurrences of motility catagories on both seamounts and the basin area.

the habitat heterogeneity in Indian Ocean 14| 'Response of benthic community structure to Megafaunafrom ^Andaman ‘Back-arc Basin incCuding seamount Chapter - 4

Stress: 0

Valley floor CSM -Sum m it ( O i

Figure 4.8. nMDS analysis of substratum types along the study sites in the Andaman Sea, the seamounts CSM and SM2, and the off axis basin.

Figure 4.9. nMDS analysis of megafaunal community along the study sites in the Andaman Sea, the seamounts CSM and SM2, and the off axis basin.

Response of Benthic com m unity structure to tfie habitat heterogeneity in Indian Ocean 115 j4egafaunafr°m JAncCaman Hack-arc “Basin incCucCing seamount Chapter - 4

(fi

Summit Flank Summit Flank Off-axial Rift valley (434 m) (594 m) (1336 m) (1357 m) highs (2897 m) (1791 m) I____ I______I I___ — i— ----1---- CSM S M 2 Basin ------!------___ I Seamounts Figure 4.10. Transect-wise distribution of megafaunal community structure indices (S: number of species, d: MargalePs index, J ’: evenness, H’: Shannon diversity).

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 116 } Megafauna from ^Andaman 'Back-arc ‘Basin incCucCing seamount Chapter - 4

Seamounts in Indian Ocean

Figure 4.11. Number of taxa reported from the Indian Ocean seamounts including the present study. A: Bezrukov, B: Equator (Indian), C: Fred, D: Lena. E: Mount Error Guyot, F: Ob' Seamount. G:Shcherbakov, H: Travin Bank, I: Unnamed Seamounts - 1234. J: Walters Shoal. K: CSM - ABB. L: SM2-ABB.

(excluding present study)

Figure 4.12. Comparison of sponges recorded from seamounts around the globe.

"Response of benthic community structure to the habitat heterogeneity in Indian Ocean 1171 Megafauna from Andaman Back-arc Basin incCuding seamount Chapter - 4

Figure 4.13. Map of Pheronema sp. distribution on the world ocean seamounts. The white circle indicates the new addition of Pheronema sp. from the seamounts in the Indian Ocean.

‘Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 1*1 Chapter 5 Megafaunal community structure in mid-oceanic ridge: habitat-scale pattern on the Carlsberg Ridge MegafaunaCcommunity structure in micC-oceanic ridge Chapter - 5

'Imagine miCCions of square mdes of a tangledjumhCe of massive peaks, sawtoothed ridges, earthquake shattered cCiffs, vaCCeys, Cava formations of every conceivahCe shape - that is the Mid-Ocean nidge."- Maurice ■Ewing (1974)

5.1 Introduction

The deep sea is considered as the largest biome on Earth and the benthic fauna represent the most abundant component life in the deep sea. Those deep oceanic benthic species are thriving mostly within soft sediments, although they include assemblages living on hard rocks of continental slopes, seamounts and mid-oceanic ridges. Mid-ocean ridges (MOR) are underwater chains of mountains that constitute the largest topographic feature on this planet extending to 75,000 km in length (Garrison, 1993) and attracted considerable attention for their fabulous biodiversity, fisheries and mineral resources (Fowler and Tunnicliffe,1997; Clark et al., 2010). Earlier biological studies over MOR mostly focused on chemosynthetic environments (Van Dover, 2000), while comparatively few studies addressed heterotrophic fauna (Felley et ah, 2008; Molodtsova, 2013). However, the recent multinational project on “Patterns and process of the Ecosystem of the Northern Mid- Atlantic” (MAR-ECO) (Bergstad and Godo, 2003; Bergstad et ah, 2008), part of global Census of Marine Life (CoML) program (McIntyre, 2010), has greatly increased knowledge on MOR environments. The Carlsberg Ridge, northwestern limb of the Indian Ocean Ridge system, is one of the least studied oceanic ridge system. Several geophysical and hydrographic surveys have been carried out (Laughton, 1967; Kamesh Raju et

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 119 \ \f v 2 v MegafaunaCcommunity structure in micC-oceanic ridge Chapter - 5 al., 2008; Murton et al., 2003, Ray et.al., 2008; 2012) in different segment of Carlsberg Ridge. However, there have been very few investigations of regional benthic fauna. Glasby, 1971 have attempted to explore the biological communities associated with the non-vent regions of the Carlsberg Ridge but no attempts have been made to quantify benthic faunal abundance or to link biological information with habitat parameters. Biological studies have mostly focused at the Kairei and Edmond fields near Rodriguez Triple Junction (Hashimato et al., 2001; Gamo et al., 2001; Van Dover et al., 2001).

The distribution of deep-sea fauna is primarily influenced by habitat (Levin et al., 2001). Heterogeneous habitats are predicted to support more complex and diverse biological assemblages (Tews et al., 2004; McClain and Barry, 2010; Gooday et al., 2010). There are several approaches to characterize and classify the seabed at spatial scales, ranging from local environment (habitat) to large ecosystems, generally referred to as habitat mapping. These approaches link habitat variables, such as nature of substratum or terrain and oceanographic settings to biological communities. Sea floor habitat mapping is an important tool for monitoring environmental change, assessing anthropogenic impact on benthic organisms, and management fisheries resources. Mapping of habitat is also useful to predict the impact of environmental parameters on benthic biota (Mortensen et al., 2009). Substratum type largely determines distributions of benthic animals (Schneider et al., 1987; Auster et al., 3 991). Benthic community patterns are often structured by factors that co-vary with depth, such as food supply (Gage and Tyler 1991). Decreases in benthic community abundance are commonly observed with depth (Pipenburg et al., 2001; Jones et al., 2007), most likely because of decreases in the availability of organic matter. Faunal distribution varies with habitat on the rocky areas of seamounts (Genin et al., 1986; Kaufmann et al., 1989; Sautya et al., 2011), continental slopes (Tyler and Zibrowius, 1992) and near hydrothermal vents (Grassle, 1986; Tunnicliffe,

•Response of benthic community structure to the habitat heterogeneity in Indian Ocean 120 11‘ :: . MegafaunaC community structure in mid-oceanic ridge Chapter - 5

1991; Van Dover, 1995). But rocky areas of non-vent region of MOR, especially in Indian Ocean, are little known. Although underwater still-photographic techniques have been productive to understanding of small-scale processes and interactions with specific environmental variables (Grassle et al., 1975; Smith and Hamilton, 1983; Schneider et al., 1987; Langton and Uzmann, 1989), they have some limitations related to noncontiguous quadrats, variability in camera height and resolution which confound statistical analysis. With the advantage of being non-destructive, the usage of underwater video technology has become a popular scientific tool (Solan et al., 2003) and is one way to increase data acquisition over limited time periods (Auster et al., 1991). In the present study, it was investigated the distribution of megafaunal communities and types of substratum through underwater video techniques which support the non-destructive method and minimized data acquisition. This study was the first in the Carlsberg Ridge area to produce underwater images of benthic megafaunal communities in a quantitative manner.

Objectives 1. To investigate benthic megafaunal community patterns with respect to bathymetric regions 2. To investigate the community patterns with small-scale habitat along the CR.

'Response of Benthic community structure to the BiaBitat heterogeneity in Indian Ocean 121 | ;• Megafaunaf community structure in micC-oceanic ridge Chapter - 5

5.2 Geophysical settings of the study area

The Carlsberg ridge, demarcating the north and northwestern part of the Indian Ocean ridge system, is accreting at the divergent plate boundary between the Somalia-India and Arabian plates (McKenzie et al., 1970). This is a typical slow spreading (half spreading rate of 11 to 16 mm/yr) ridge having a V-shaped well-defined deep (> 4000 m) rift valley with wide valley floor, steep side-walls and several transform faults. Kamesh Raju et al. (2008) surveyed the segmentation patterns of Carlsberg Ridge between 62°20’E and 66°20’E using swath bathymetry and magnetic data. This survey revealed rugged topography with steep valley walls, ridge parallel topographic fabric, and axial volcanic ridges. Seabed depths in these geophysical provinces range from 1600m to more than 4000m and likely represent a variety of ecological zones. For present investigation, seafloor surveys were carried out over two ridge segments which include areas of unusually large episodic event plume (CR-2003) between 5° 10’ and 6°00’N (Murton et al., 2003; Ray et al., 2008) and potential hydrothermal activities between 3°30’ and 4°00’N (Ray et al.,

2012).

5.3 Materials and Methods In November, 2007, the RV Sonne (RVS-2) was used to survey two segments of the Carlsberg Ridge. As a part of this program we investigated benthic megafaunal communities and their distribution patterns among different geophysical settings (e.g., off-axial highs or mounds, valley wall and floor) of these two ridge segments (Figure 5.1). During the cruise a Television guided grab (TVG) and Ocean Floor Observation System (OFOS) were operated over 8 and 3 transects respectively (Table 5.1). EM 120 multi beam bathymetry data was obtained on the same cruise and used to decide the survey locations. Three TVG transects (TVG 1, 2 and 3) were carried out within different part of large event plume area in the northern segment (Figure 5.1). The first survey (TVG 1) was along the deep valley floor, while two

■ Response of benthic community structure to the habitat heterogeneity in Indian Ocean 122 | >> , * « MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5 others (TVG 2 and TVG 3) were on the corner highs near a transform fault. Another four surveys (TVG 4, 5, 6, 7 and 8) were in the southern segment, mostly over the deep valley floor (depth >3000 m). All three OFOS transects were located close to the rift valley wall near the valley floor.

The benthic Megafaunal communities were observed using video transects collected with the camera attached with TVG and OFOS (Plate 5.1). Both were operated from the starboard side of the ship. The OFOS seabed imaging platform was flown with a real-time video link to the surface (digital through a fiber optical LWL cable). The position of OFOS was recorded continuously with reference to an Ultra-Short Baseline Navigation transponder. It has three cameras: one PFJOTOSEA 5000 stereo-camera (that obtains two simultaneous photographs), one color video (DSPLMSC 2000 colors with parallel red lesser, mounted 100 mm apart were used for scaling) and one monochrome video camera (OSPREY 0111 -6006 B/W) and lighting (4xROS QL 3000 and/or 2xDSPL Arc-light). The TVG system had similar capacity to OFOS and had two video cameras (lxDSPLMSC 2000 color, and IxOSPREY OE 1390 monochrome digital video), lighting (4xROS QL 3000) and telemetry. All the still photographs and video images were collected on DVD at the surface. TVG was towed along the predefined track at the speed of about 0.5 to 0.7 knots while OFOS was operated at 0.2-0.5 knots. The cameras of both the systems obtained images at a height (altitude) of 1 to 5 m (depending on the seabed substratum) above the seabed.

Image processing and Data analysis All megafauna were identified from images at highest possible taxonomic resolution with additional help from experts (see acknowledgements). Owing to the nature of image material, it was not possible to identify all animals to species level. Morphologically distinct organisms were identified and labeled by unique names referring to the taxon,

‘Response o f Benthic comntunity structure to the habitat heterogeneity in Indian Ocean 1231 f a g. t MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5 such as Hexactinellida sp. 1, Hexactinellida sp.2 or Holothuroidea sp. 1 etc. Seabed substratum was classified into distinct habitats.

The habitat type, presence and identity of all organisms was recorded along each transect. Positional information for each photographwas obtained from the navigation data. As navigation data were noisy the data were smoothed and total transect length was measured manually in ArcGIS software. This measured length was used for subsequent area calculations. The width of the transect was ascertained from the laser scalers visible in each image (for OFOS) and from camera altitude (for TVG). For OFOS, the distance between laser scalers in 50 randomly selected frames (in case of OFOS) was measured and the mean used to estimate transect width. For TVG, transect width was calculated from mean camera altitude using the following equation: Width of transect, W — 2 x tan (a/2) x camera altitude (H ). Where, a is angle of focal length (20°) o f the camera. The area coverage of each transect was estimated from the total length (L) and width (W) as follows: Area {A) = L * W

Statistical analysis Only those species that could be confidently identified were included in the analysis. The data were subjected to univariate analyses to study the benthic community structure, using Margalefs index (Margalef, 1968) for species richness (d), Pielou’s index (Pielou, 1966) for species evenness (J’), and the Shannon-Wiener index (Shannon and Weaver, 1963) for species diversity (FT by using loge). To investigate how similarity between assemblages changes with the bottom substrata and bathymetric gradients in the Carlsberg Ridge, several multivariate analyses were conducted using PRIMER v6 (Clarke, 2006). Following the general recommendations of Clarke and Warwick (2001), the Bray-Curtis similarity measure was employed to

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 124 | i* a ” c MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5 assess multivariate similarity and dissimilarity between transects based on log-transformed faunal abundance data. The differences between transects groups was assessed with multivariate analysis and represented the nMDS (non-metric Multi-Dimensional Scaling (nMDS)) and the organisms which most contributed to the observed similarity within and dissimilarity among groups were assessed using SIMPER (similarity percentage).

5.4 Results

Habitat structure Habitats variability was greatest in the deeper areas of the rift valley (Figure 5.3), varying from exposed pillow basalts to fine sedimentary cover on rocky substratum. These habitats can be classified into 12 different types of seafloor substratum over eleven TVG and OFOS transects located within our study area (Figure 5.2).

Shallower transects (TVG 2 and TVG 3) (Figure 5.3) Two shallower transects (TVG 2 & TVG 3), located on off-axial highs, have mostly basalts covered with sediments. The seafloor along the TVG 2 transect was predominantly basaltic basement covered with sediments (H3), with some areas covered with sediment only. Transect of TVG 3 was mostly comprised of basalt with sediment type habitat HI with a small percentage of glass extruded basalt with sediments (H2) observed.

Deeper transects (OFOS 1, 2 & 3; TVG 1,4,5,6,7 & 8) (Figure 5.3) Only two habitat types were observed at the transect TVG 1, while other deeper transects had greater habitats variety. The habitat H11 (exposures of basalts in a thick sediment covered plain) was dominantly observed throughout the northern segment deeper transect TVG 1. Other TVG transects (TVG 6, 7 and 8) located in the deeper region had predominantly sediment

'Kesjjonse of Benthic community structure to the BaBitat heterogeneity in Indian Ocean 125 | f c. MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5 habitats (H5) except TVG 4 (H2 dominant) and the TVG 5 (HI [Pillow as well blocks of basalts with sediments] dominant). Six varieties of habitats were observed in transect OFOS 1. The habitat H3 was dominant, representing 32.7% of the transect, while habitats HI, H5 and H2 altogether covered about 60% of area of the transect OFOS 1. Habitats, H7 (another type of pillow basalt with tubular shape) and H10 (talus or broken pillow basalt fragments) were observed rarely. Four varieties of habitats were seen at the transect OFOS 2. 62.5% o f OFOS 2 transect comprised habitat H5 while remaining 8.33%, 18.63% and 10.49% were occupied by HI, H2 and H3 habitats respectively. Maximum varieties (nine) of habitat have been observed along the OFOS 3 transect. Habitat H5 had 24% coverage throughout the transect, while other habitats such as HI, H3, H10, H11 (exposures of basalts in thick sediment covered plain) and H12 (pillow lavas covered with thin sediment cover) jointly contributed 68% of the area of this transect.

Megafaunal assemblage composition A total of 2090 individuals (13% at shallower and 87% at deeper areas) from 90 taxa and morphotypes, representing 7 phyla, were observed in the underwater video and still images in the two segments of the CR. On average the megafaunal population was dominated by cnidarians, comprising up to 42.27% of total faunal abundances. Echinodermata and Porifera were the next most dominant group, contributing up to 21.15% and 20.86% in the shallower and deeper areas respectively. The cnidarians were mostly observed in shallower transects, where 73.21% (TVG 3) and 61.25% (TVG 2) of the megafauna were cnidarians (Fig. 4). In both shallow transects the cnidarians were predominantly Gorgonian sp2. In contrast, the deeper transects contained a maximum of six megafaunal groups and dominated by echinoderms (31.57% of total population). The group in deep water includes Porifera, Arthropoda, Chordata and Cnidaria. Porifera were dominant at transect OFOS

'Response of Bentfiic community structure to tfie fiuBitut fieterofleneity inlncCiun Ocean 126 ( T :* z i MegafaunaCcommunity structure in mid-oceanic ricCge Chapter - 5

1 and OFOS 3, contributing 92.09% and 32.95% respectively (Figure 5.4). Echinodermata showed the highest contribution to the total megafauna (93.18%) at the transect TVG 1. The majority of echnioderms were Echinoidea sp2. Echinoderms were also dominant over transects TVG 5, 7 and 8, contributing 42.85%, 34.42% and 26.31% of the total fauna at each transect respectively. Holothurians were mostly present in this group. In OFOS 2 arthropoda comprised 46.15% of the megafaunal population. They were also observed on all other deeper transects (except TVG 4). The short transect of TVG 4 was occupied by only a few cnidarians. At TVG 6 Chordata had the highest densities, comprising 35.89% of total population of the transect. However, this group was well documented throughout the CR region. Other megafaunal groups, such as xenophyophores and Annelida were occasionally observed in both the segments. Besides depth and type of substratum, the near bottom water may possibly have control over such faunal group composition. Although the shallower transects temperature are more warm than deeper transect, it was also noticed that overall faunal composition and a higher diversity of fauna inhabited relatively warm (1.9 - 1.97°C) water; whereas fewer species occurred in cooler (~1.8°C) areas (e.g. TVG 1, TVG 4 and OFOS 1).

Megafaunal density and diversity: constraints on habitats The population density varied between 5.68 and 171.34 ind.1000 m 2 with a mean of 37.98 ± 3.31 ind.1000 m'2 in the study area (Figure 5.5). 272 individuals were seen at the shallower transects, and the remaining (1818 individuals) observed in the deeper transects. However, megafaunal densities were higher at shallower transects than deeper transects. Density varied from 60.81 to 171.34 ind.1000 m'2 (mean 116.07 ± 55.26) in the shallower transects and from 53.53 to 5.68 ind.1000 m'2 (mean 20.63 ± 15.98) in the deeper transects. The highest density was observed along the shallow transect TVG 3, while the lowest was in the deeper area (transect OFOS 3). The maximum

'R&SJ90TIS6 of Bent (He com m unity structure to tBe BczBitut Beterofleneity in JncCicin Ocecm 1271 v a z MegafaunaCcommunity structure in micC-oceanic ridge Chapter - 5 numbers of individuals (1531) was found on the OFOS 1 transect, while the lowest number (3) was observed on the TVG 4 transect. The highest number of species (S = 57) was observed at the deeper transect OFOS 1, while the lowest (1) was recorded in the transect TVG 4 (Figure 5.6). M argalef s index (d) of species richness varied from 0.0 to 14.07, the higher value recorded at the transect OFOS1 and the lower at the TVG4. Pielou’s index (J’) of evenness varied from 0.28 to 0.93, with higher values at TVG 8 and lower value shown at TVG 1. Values of IT varied from 0.39 to 2.28 while higher value recorded at TVG 7 and lower at TVG1 along the study area.

Faunal densities were highest on the pillow lava with less sediment (habitat type: H8) at the transect OFOS 1 and minimum densities occurred on the similar pillow basalts with sediments (habitat type: HI) in deeper areas (OFOS 3). Sedentary megafaunal assemblages, dominated by cnidarians and poriferans, characterized the hard substratum habitat (H8 habitat). On the other hand, mobile groups, such as Echinodermata, were comparatively abundant in finer-grained sediments, such as those found in habitat HI, H5, H9, HI 1 (abundant at transects TVG 6, TVG 7, TVG 8; Figure 5.3).

Multivariate analysis: Groupings o f habitat based on nature o f substratum, water depth and faunal community

The non-Metric Multi dimensional scaling approach, based on the average percentage o f substratum types, separated two groups, with ~40% similarity from hierarchical clustering (Figure 5.7). Shallower transects (TVG2 and TVG3), located on the off-axial highs, formed Group 1, where HI contributed the highest similarity percentage (Table 2) at this depth region. The habitats which had mostly mixed sediments (e.g., HI, H2, H3, H5), form another cluster (Group 2) with deeper transects on the valley floor areas. Dissimilarity between the groups were observed because of HI and H5

Response of Benthic com m unity stTuctuTe to the BuBitcit Betevo^eneity in IncCian Ocean 128| P a % c. MegafaunaC community structure in micC-oceanic ridge Chapter - 5 substratum types, where HI made highest contribution at shallower depths and H5 highest contribution at deeper depths (Table 5.2). Cluster analysis, based on average density of megafauna also made a clear distinction (<5% similarity) between the depths. Group A comprised the shallower transects (TVG 2 & TVG 3) and the deeper transects (OFOS 2, OFOS 3, TVG 1, TVG 2, TVG 3, TVG 5, TVG 6, TVG 7 & TVG3) made a second grouping (Group B; Figure 5.8). Overall Goronian sp2, Brisingid sp2, Gorgonian spl, Actinaria sp3 and Hexactinellida sp21 were restricted to shallower tansects and responsible for >90% of the differences which separated Group A. Plesiopenaeus spl, Holothuroidea sp8 and Holothuroidea sp5 were restricted to the deep transects and the major contributors (total 73%) to Group B (Table 5.3).

Relationship between type o f habitat and megafaunal community

A negative relationship was observed between faunal density and water depths (Figure 5.9). However, density had positive relationship with habitat types HI (Table 4). Number o f species (S) showed a positive relationship with pile of pillow basaltic habitat H7. Highest number of species was recorded along OFOS 1 whereas minimum over TVG 4 which result from variation in the area coverage between the transects. This was reflected during regression analysis between total faunal count and area covered by habitats (Figure 5.10). A positive relation also found between Margalef s Index (d ) and the amount of habitats H3 and H7. A negative relationship was observed with biodiversity (Shannon-Wiener index ( //’)) and habitats (seen in H4 and H10).

tfie habitat heterogeneity in Indian Ocean 129 | P e 'Response of Benthic community structure to MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5

5.5 Discussion All transects observed had basalts present. Some observations, for example the H10 habitat, included talus or broken pillow basal fragments at the base of small mounds, which may suggest tectonic activity at the area. The segmentation pattern of the Carlsberg Ridge between 62°20'E and 66°20'E has been investigated using swath bathymetry and magnetic data (Kamesh Raju et al., 2008). The multibeam mapping tool revealed rugged topography with steep valley walls, geo-morphological structures such as ridge-parallel topographic fabric, and axial volcanic ridges. Further some substrata, such as H5 and HI 1, were mostly covered with pelagic sediments, reworked by benthic fauna (such as observed at transect TVG7). Laughton (1967) also observed similar types of substratum and suggested benthic activity during underwater photography along the Carlsberg Ridge. The general morphology of the Carlsberg Ridge sections used in the present study is similar to the Mid Atlantic Ridge between Kane and Atlantis transform (Kamesh Raju et al., 2008). In the present study higher mean faunal density was observed at shallower transect located at off-axial highs area, while comparatively lower density and higher diversity were observed at the deeper transects. Glasby (1971) studied the western flanks of the Carlsberg Ridge and revealed with extensive biological activity, characterized by large scale burrowing of sediment and the appearance of worm casts, brittle stars and holothurians. However, there are no quantitative data available on benthic megafaunal community to compare the present study in Carlsberg Ridge. Comparatively less species recorded in the present study than MAR, which is due to variation in number of attempt to study from both the region. Benthic invertebrates megafauna were reported more than 650 species in MAR, while fauna attached to hard substrata such as cnidarians and poriferans found 112 and 35 number of species respectively (Vecchione et al., 2010). It was suggested that bathymetry can influence faunal distribution ‘directly’, through physiological tolerance of pressure

'Response o f BentfHc com m unity structure to the fi&Bitcit Beteyopjeneity iyi IncCiun Ocsctn 130 |F v<. " i MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5

(Seibenaller and Somero 1978) and high pressure requirement for larval development in some species (Young and Tyler 1993) or may be ‘indirectly’ by representing covariance with another environmental variable, such as temperature of water mass (Gage and Tyler 1991). In the present study , density showed negative relationship with increasing depth. Decreases in faunal abundance with depth occur in most deep-sea communities investigated (e.g, Carney, 2005; O’Hara, 2008; Wiliams et al., 2010). It was suggested that global faunal abundance and biomass showed an exponential decline with increasing depth (Rex et al., 2006).

The result of cluster analysis of faunal density reflected the habitat pattern and their associated faunal communities. Cnidarians especially Gorgonian sp2, which is sedentary in nature, attaches to rocks and is dominant at shallower depths. Cnidarians were also found at all MAR-ECO sites inspected with ROVs at the depths between 800 - 2,400 m, but were most common at 1400 m (Vecchione et al., 2010). Further Plesiopenaeus sp.l and Holothuriodea sp.8 sp were dominant at deeper transects where substrata were mostly fine sediments. Plesiopenaeus species was found just above the muddy abyssal floor at the depths of 3000 m during underwater video survey by SERPENT project off Goa, Arabian Sea (Jones et al., 2009). Small-scale distribution patterns of deep-sea megafauna in Charlie-Gibbs fracture zone of Mid- Atlantic Ridge showed Porifera and Cnidaria were mostly associated with rocky substrata while holothurians mostly occurred on sediment covered plains (Felley et al., 2008). Holothurians are deposit feeders reworking sedimentary particles (Gray 1974; Rowe et al., 1974).

Porifera mostly appeared on H7 type habitat while cnidarians were found in higher abundances on hard substratum of H1 habitat. Cnidarians were predominantly observed at shallower transects, which mostly covered with habitat HI. Deep-sea poriferans and cnidarians are suspensivorous sessile

"Response of Benlfxic copnmxinity stvuctuve to tfie fiaBitat Betevofjeneity in Indian Ocean 1311 P n » a MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5 fauna, mainly found to settle on suitable hard substrata and live in areas with local water currents to supply food particles from surface ocean (Hogg et al., 2010) . This hard substrate environmental factor also determined their abundance and distribution (Rice et al., 1990). Echinodermata and Arthropoda had maximum abundance on sediment mixed substratum particularly H9 and H5 type of habitat at valley floor area. Other groups like Annelida and Xenophyophorea showed positive relation with H 11 and H3 habitats respectively. The free swimming chordata did not show any relation with habitat. Poriferans were most abundant at the transect OFOS 1 which resulted from high numbers of Hexactinellida sp.3. Although overall abundances were higher at H8 habitat at OFOS 1, the species Hexactinnelida sp.3 was mostly seen on the H7 basaltic hard substratum habitat. As a result, poriferans showed positive correlation with this habitat (Table 5.4). Cnidarians had the greatest relative abundances (Figure 5.4) at the transect TVG 4, where the habitat H10 was dominant, as would be predicted from the species-area relationship. In general, the echinoderms Holothuroidea sp.8 and Holothuroidea sp.5 contributed most to total abundance at the deeper transects and were mostly seen with sediment type habitat H5. Owing to the dominance of Echainodea sp.2, the group Echinodermata showed significant positive correlation with habitat H9.

5.6 Biological potential of Carlsberg Ridge Some dredge samples have been collected during the scientific cruise ‘Akademic Bois Petrov’ at Carlsberg Ridge in 2009. A new genus and species of hexactinellid sponge has been discovered from these samples (Sautya et al., 2011) . Benthic diversity studies on non-chemosynthetic ecosystems have been conducted at the southern most of the South Atlantic MAR system (see Polar Biology, 2006: 29, special issue). These studies found that diversity was much higher than previously recorded especially for echinoderms, molluscs,

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 132 | : ? t. MegafaunaCcommunity structure in micC-oceanic ridge Chapter - 5 cheilostome bryozoans and amphipods and many of these records were new to the science. About 10% of species in MAR-ECO epibenthic invertebrate species appeared to be new to the science (Vecchione et al., 2010). As the Carlsberg Ridge is one of the less studied areas among the ridge located in the world ocean, so there is high scope to explore new biological communities which possibly not known to the science.

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 133 | v Table 5.1. Details of underwater video observation and their geographical locations along the Carlsberg Ridge, Indian Ocean Station ID Duration ( Date & Time) Start Location End Location Depth Bottom Area UTC (Latitude N/ Longitude (Latitude N/ range(m) temperature covered E) Longitude E) (°C) (* CTD (m2) failed) Shallower * T V G -2 25/10/2007; 04:29 to 05° 26.5137 61u26.524' 05° 27.0717 1643 - 1486 2631 25/10/2007;09:20 61 °26.193' * TV G -3 25/10/2007; 09:34 to ~05°26.4527 61u 26.578'~ 0 5 u 26 .6 8 4 7 1 8 3 4 - 1656 65 3 .6 6 4 25/10/2007; 12:10 61°26.459' Deeper

TVG-1 24/10/2007; 17:10 to 05°51.932’ / 6 1 °1 1.203’ 05° 52.3917 3628 - 3676 1.81 1509.62 24/10/2007; 20:19 6 1 °1 1.695' TV G -4 03/11/2007; 22:41 to ~03°58.5057 63° 01.000 03° 58.5567 3558-3365 1.90 203.412 04/11/2007; 02:00 6 3 °0 1.041' TV G -5 11/11/2007; 09:55 to 03° 4 0 .2 9 1 ' / 63“ 44.794~r ~ 03° 39.7497 6313 3339 - 3413 1.90 1324.468 11/11/2007; 14:58 45.032' T V G -6 12/11/2007; 17:15 to ^03° 40.3257 63“ 45.156r~ 03° 39.8217 6315 3565 - 3436 1.90 2 2 5 8 .1 0 4 12/11/2007; 23:16 45.026' T V G -7 13/11/2007; 00:38 to ~03° 39.649' / 63u 44.474r~ 03° 40.1447 63® 3 6 6 9 - 3 4 1 7 1.91 1758.12 13/11/2007; 04:14 4 4 .9 0 7 ’ T V G -8 13/11/2007; 06:52 to 03u 40.3567 63° 44.958' 03° 40.0097 63° 3 5 8 9 - 3529 1.91 2488 .2 4 6 13/11/2007; 11:51 44.779'

'Response o f HentHic community structure to tde HaHitat Heterogeneity in Indian Ocean 134 f l> » e <• O FO S - 1 29/10/2007; 21:00 to 05° 13.647'/61° 58.616' 05” 14.304'/61° 3513 - 3548 1.82 1 2 8 5 9 8 7 5 5 \ 30/10/2007; 08:16 5 8 .5 9 2 '

O FO S - 2 06/11/2007; 11:08 to 03° 47.932'/63° 37.594' 03d 47.7587 63° 3 2 7 2 - 3291 1.95 1 0 8 0 .4 8 5 06/11/2007; 14:47 3 7 .7 3 9 ’ O FO S - 3 06/11/2007; 16:24 to “ 03° 47.7867 63° 37.736’ 03° 45.0577 63° 3288 - 4236 1.97 15470.51275 07/11/2007; 03:26 3 7 .2 6 5 ’

Table 5.2. SIMPER analysis of Habitats in Carlsberg Ridge area; average abundances (Av. Abund), average Similarity (Av. Sim), Average Dissimilarity (Av. Diss), contributed percentage (Contrib.%) and cumulative contribution (Cum%). Average similarity Group 1 Habitat Av.Abund Av.Sim Contrib% Cum.% HI 90.52 82.87 100 100 H2 0.92 0 0 100 H3 7.4 0 0 100 H5 1.16 0 0 100 Group 2 Habitat Av.Abund Av.Sim Contrib% Cum.% H5 50.53 36.61 62.06 62.06 HI 18.95 12.63 21.4 83.46 H3 14.42 7.93 13.44 96.91 H2 5.1 1.31 2.22 99.13 Average dissimilarity Group 2 Group 1 Habitat Av.Abund Av.Abund A v.D iss Contrib% Cum.% HI 18.95 90.52 35.78 48.19 48.19

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 13S| I' . H5 5 0 .5 3 1 .1 6 2 4 .6 8 3 3 .2 4 _ 8K 43~1 H3 14.42 7.4 5 .8 7 7 .9 1 8 9 .3 4 H2 5.1 0.92 2.42 3.26 92.59 H10 3.84 0 1.92 2.58 95.18 HI 1 2.09 0 1.05 1.41 96.59 H12 1.87 0 0.93 1.26 97.84 H7 1.16 0 0.58 0.78 98.62 H9 1.16 0 0.58 0.78 99.4 H4 0.74 0 0.37 0.5 99.9 H6 0.12 0 0.06 0.08 99.99 H8 0.02 0 0.01 0.01 100

Table 5.3. SIMPER analysis of megafaunal abundances in Carlsberg Ridge area; average abundances (Av. Abund), average Similarity (Av. Sim), Average Dissimilarity (Av. Diss), contributed percentage (Contrib.%) and cumulative contribution (Cum%). Group A, Average similarity: 48.13 Species Av.Abund Av.Sim Contrib% Cum.% Gorgonian sp2 41.05 18.01 37.41 37.41 Brisingid sp2 12.21 7.86 16.33 53.74 Gorgonian spl 12.21 6.55 13.61 67.35 Actinaria sp3 9.16 6.55 13.61 80.95 Hexactinellida sp21 8.01 4.58 9.52 90.48 Group B, Average similarity: 23.19 Species Av.Abund Av.Sim Contrib% Cum.% Plesiopenaeus spl 2.59 11.98 51.64 51.64

•Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 1361 p « « <- | Holothuroidea Sp8 1.4 3 .4 2 1 4 .7 5 6 6 .4 Holothuroidea sp5 0 .6 4 1 .5 4 6 .6 5 7 3 .0 5 Unidentified chordate sp5 1.89 1.3 5.61 78.65 Hexactinellida spl6 0.51 0.83 3.6 82.25 unidentified Brachyuran spl 1.61 0.83 3.57 85.82 Unidentified chordate sp2 0.41 0.63 2.73 88.54 Anguiliformes sp2 0.7 0.47 2.04 90.58 Groups B & A, Average dissimilarity = 98.96

Group A Group B Species Av.Abund Av.Abund A v.D iss Contrib% Cum.% Gorgonian sp2 41.05 0 29.81 30.12 30.12 Brisingid sp2 12.21 0 9.98 10.08 40.21 Gorgonian spl 12.21 0 9.4 9.5 49.71 Actinaria sp3 9.16 0.06 7.72 7.8 57.5 Gorgonian sp3 12.62 0 6.99 7.07 64.57 Hexactinellida sp21 8.01 0 6.3 6.36 70.93 Hexactinellida spl8 6.11 0 3.83 3.87 74.8 Whip coral sp2 6.31 0.26 3.37 3.41 78.21 Echinoidea sp2 0 4.01 3.23 3.26 81.47 Plesiopenaeus spl 0 2.59 2.37 2.4 83.87 Unidentified chordate sp5 0 1.89 1.56 1.58 85.44 Hexactinellida spl9 1.53 0 1.39 1.41 86.85 unidentified Brachyuran spl 0 1.61 1.3 1.32 88.17 Anguiliformes sp4 0.95 0 1.23 1.25 89.41 Holothuroidea Sp8 0 1.4 1.21 1.23 90.64

:Kesjjonse of Benthic community structure to the BaBitat heterogeneity in Indian Ocean 137J P Table 5.4. Correlation between habitat types and megafaunal groups, biotic indices (values i in bold and italics are significant) HI H2 H3 H 4 H 5 H6 H 7 1 H 8 H 9 H 1 0 H I 1 H 1 2 A bundances .8159 -.0619 -.1619 -.2409 -.4288 -.1955 .1076 0 -.0813 -.2842 -.2713 -.2234 p= .002 p=.856 p = 6 3 4 p=.475 p=.188 p=.565 p=.753 p=.753 p=.812 p=397 p=.420 p=.509 .1034 .3617 .6754 -.3502 -.0189 -.1147 .9298 -.2396 -.3345 .0823 .1089 p=.762 p=.274 p= .0 2 3 p=.291 p=.956 p -.7 3 7 p=.0Q01 p=.478 p=.315 p=.81Q p=.750 D -.0688 .3109 .5849 -.3924 .0888 -.0346 .7 5 0 6 -.2491 -.2735 .4993 .5033 p=.841 p=.352 p - 0 5 9 p=.233 p=.795 p=.920 p = .0 0 8 0 p=.460 p=.416 p = 1 1 8 p= .l 15 J' .2760 .1826 .0355 -.6535 .6523 .2416 -.2328 0 -.4253 -. 7833 .1234 .0599 p = .4 1 1 p=.591 p=.917 p = .029 p= .030 p=.474 p- .491 p=.491 p=. 192 p = .004 p=.718 p=.861 H' (L og e) .3545 .1936 .2402 -.6958 .5552 .1330 .0679 0 -.5577 -. 7712 .2405 .2005 p=.285 p=.569 p=.477 p - .0 1 7 p=.076 p=.697 p=.843 p=.843 p=.075 p = .005 p = 4 7 6 p ~ 5 5 4 Xenophyophorea -.0409 .4047 .6760 -.1308 -.0972 -.1190 1.0000 -.1099 -.1562 -.1228 -.1000 p = 9 0 5 p=.217 p=.022 p=.702 p=.776 p=.727 P= — p=0.00 p=.748 p=.647 p = 7 1 9 p=.770 Porifera .3568 .3207 .4962 -.2244 -.2725 -.1965 .8956 -.1848 -.2526 -.1602 -.1310 p=.281 p=.336 p=. 121 p=.507 p=.417 p=.562 p= .001 0 p=.587 p=.454 p=.638 p=.701 C nidaria .8519 -.1583 -.3172 -.0953 -.4621 -.1537 -.1309 -.1309 -.1542 -.1322 -.1705 -.1393 p=.Q01 p=.642 p=.342 p=.781 p=.152 p=.652 p=.701 p=.701 p=.651 p=.698 p=.616 p = 6 8 3 Echainodermata .2648 -.2973 -.4063 -.3222 -.3730 -.0976 -.2465 0 .7 2 7 5 -.2727 -.3139 -.2604 p=.431 p = 3 7 5 p=.215 p=.334 p=.259 p = 7 7 5 p=.465 p=.465 p= .011 p = .4 17 p=.347 p=.439 A nnelidea -.1880 -.0634 -.0162 -.1308 -.0889 .0890 -.1000 0 -.0201 .1576 .9730 1.0000 p=.58Q p=.853 p=.962 p=.702 p=.795 p=.770 p=.770 p=.953 p=.644 p=.000 p= — A rthropoda -.3894 .2589 .1466 -.2041 .7626 .1389 -.1616 0 -.2083 -.3140 -.1205 -.0946 p = 2 3 7 p=.442 p=.667 p = 5 4 7 p= .006 p=.684 p=.635 p=.635 p = 5 3 9 p=.347 p=.724 p = 7 8 2 C hordata .1591 -.0947 -.1360 -.3343 .5186 -.0653 -.3080 0 -.2157 -.4230 -.3262 -.2893 p=,640 p=.782 p=.690 p=.315 p=.102 p = 8 4 9 p=.357 p=.357 p = 5 2 4 p=.195 p=.328 p=.388

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 138 | i‘ MegafaunaC community structure in micC-oceanic ridge Chapter - 5

61W 61 ”30' 6200 62 30' 6300 63°30'E 64=00 64=30 65'00' 65°30' 6600' 66=30

20”

10”

0°

II ■ I

:Response of benthic com m unity structure to the habitat heterogeneity in Indian Ocean 139 | V si a c

l l , a . ' MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5

Figure 5.2. Habitat guides o the study area: HI- Pillow as well blocks of basalts with sediments on a gradual slope; H2- Pillow basalts exhibiting chilling cracks of the glass of extruded basalt with sediments; H3- A small deep with thick sediment pile bordered by an escarpment of basalts; H4- The slope along a wall and exposures o f pillows can be seen projecting out on the wall surface; H5- Sediments , the depressions within the axial valley are filled with the sediment; H6 - Sediments - Surface structures ripple marks; H7 - Basalts; Another type of pillow basalt with tubular shape overlying the pillow along a sharp escarpment. A pile of pillow basalts; H8 -Pillow lava; Thick pile or mound of pillow basalts with less sediments; H9 - Pillow lava covering with sediments; A small escarpment with coating of sediments of different thickness as per the ledge extension. Might be a fault escarpment as pillows are not visible; H10 - talus or broken pillow basalt fragments might be at the base of a scarp or small hillock. This suggests a tectonic activity; HI 1- Exposures of basalts in thick sediment covered plain; H I2- Pillow lavas covered with thin sediment cover

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 140 | P a a e MegafaunaC community structure in micC-oceanic ridge Chapter - 5

Figure 5.3

O F O S3 a - H yalonem a sp; b - Paelopatides sp; c- Asteroid sp2

O FO S2 a - Holothuroidea sp.3; b - Hexactinnellida sp.l 1; c- Plesiopenaeus sp 1

OFOS 1 a - Hexactinnellida sp7; b - Hexactinnellida spl4; c- Holothuroidea sp l; d - Hexactinnellida sp3

■Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 141 11’ :i 2 e MegafaunaCcom munity structure in micC-oceanic ridge C h apter - 5

T V G 3 a & b: Brisingid sp2. c: Gorgonacea sp2 (Whip coral)

T V G 2 a: G orgonian sp l, b: Gorgonian sp2

T V G 1 Echinoidea sp.2

. , „ .,,,, habitat Heterogeneity in Indian Ocean Response of 6entHic com m unity structure to tn 142 | 1* MegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5

T V G 6 a: Hexactinellida spl 5, b: Peniagone sp, c Paelopatides sp

TVG 5 a: Plesiopenaeus s p l , b: Anguiliformes sp2, c: Brisingid spl

TVG 4 a: Whip coral spl

Response of benthic com m unity structure to the Habitat Heterogeneity in Indian Ocean 143 | l’ a je c MegafaunaCcommunity structure in micC-oceanic ridge Chapter - 5

TVG 7 a: Peniagone sp, b: Echinoidea sp2, c: Paelopatides sp, d: Ophiuroidea sp4

63'44-30-E 6 3 °4 5 ’0"E

6 3 *4 5 0 *E

3*40 3(TN 3’ 40 '3 0 'N

TVG 8 a: Hexactinellida spl6, b: Peniagone sp, c: Plesiopenaeus spl

3 *40‘0"N 3'40-OTM

6 3 * 4 6 V E

Figure 5.3. Habitats distribution, composition, dominant habitat and species associated to suitable habitat types along the transects. All are mentioned above (OFOS 1 to TVG 8)

'Response of benthic community structure to the habitat heterogeneity in Indian Ocean 144 | P a S t 1

MegafaunaC com munity structure in micC-oceanic ricCge Chapter - 5

Deeper Sahllower Transects

Figure 5.4. Megafaunal group composition along the study area

“Response o f Hentfiic com munity structure to tfte fiuHitcit Heterogeneity in Indian Ocean 145 | I * .1 ” c MegafaunaC community structure in micC-oceanic ridge Chapter - 5

Figure 5.6. Megafaunal diversity along the transects.

20 Stress. 0 03

Group 2

/ ^ O F O S 2 \ / \

Group 1 PFOS1 TVG6 \ \ TVG 5 j (fvG ^

TVG^j \ O F O S ^ iTVG3 J

(fv G ^

Figure 5.7. nMDS of habitat types along the CR

Figure 5.8. Cluster analysis of megafaunal communities along the study area

o f » — U stroctur. to * . fotaot <» <*“ ” 146 | tMegafaunaCcommunity structure in mid-oceanic ridge Chapter - 5

Figure 5.9. Relationship between water depths and faunal abundances in the study area.

Figure 5.10. Relationship between faunal total count and area occupancy

'Response of benthic com m unity structure to the habitat heterogeneity in Indian Ocean 147 | P a g e Plate 5.1. Techniques used for sampling in Andaman Back-arc Basin and Carlsberg Ridge, Indian Ocean

a: The ship R V S o n n e used for onboard sampling; b: Television Gripper (TVG) ready for lowering from starboard side of the ship; c: TVG lowering into the water; d: Ocean Floor Observation System (OFOS) used for under water video survey and still images capturing; e: underwater live video observation and controlling unit onboard Chapter 6 Discovery of species "Discovery of species Chapter - 6

Thefirst step? in wisdom is to /enow the things themsefves; this notion consists in having the true idea o f the oh/ect; oh/ects are distinguished'ancfhnown hy their methodicaf cfassification ancf cippropriate naming; therefore Cfassification ancfShaming w iff he the foundation o f our Science.- Linnaeus (1735), quoted in Stevens (1994:201)

6.1 Introduction

Carl Linnaeus, the father taxonomy, published the first edition of his Systema Naturae in 1735. He persisted with his immense project and compiled 12 editions of the Systema Naturae before his death in 1777. In this book he was succeeded by his students and other systematists who were explored the treasure trove of specimens collected by the great eighteenth- and nineteenth- century expeditions into the exotic, unknown regions of the planet. Today, more than two hundred and fifty years later, most of unexplored habitats such as forests, mountains, marine habitats have been populated, developed, and well connected to the rest o f the world by modern techniques. The amount of wilderness remaining has shrunk to about one-third of Earth’s land surface (McCloskey and Spalding 1989), much of that third in the Arctic or Antarctic. After 90’s it was estimated that the number of known species of eukaryotic organisms is to be about 1.4 million (Lean et al. 1990; Systematics Agenda 2000 1994). It seems reasonable to suppose that most of Earth’s species have been described. But this is far from true. There are millions of species still to describe and an increasing amount of concern over whether we can discover them before they become extinct (Roberts 1991; Vane-Wright et al. 1991).

6.2 Necessity of species description Biodiversity has an intrinsic value to humans and it performs a number of ecological services for humankind directly or indirectly that have economic, aesthetic or recreational value. A large part of biodiversity is still unknown,

'Response of Bentfiic com m unity stvucture to tfie faB itat fieteTOfjeneity in Indian Ocean 14811* a Discovery of species Chapter - 6

and it is estimated that, at the current pace, it will take several centuries to describe all species living on Earth. In the context of the ongoing ‘sixth extinction’, accelerating the completion of the inventory of living biota is an issue that reaches far beyond the taxonomic community. However, the factors that influence the accretion of known species remain poorly understood. Our knowledge of the taxonomy of marine organisms, in particular, is far from complete, perhaps because most of them are hidden from our sight in an environment inhospitable to human bodies (Earle 1991). In the past few decades new kinds of sampling techniques included modernization of dredges, cores, scuba diving, underwater video survey by manned and unmanned submersibles etc. have changed our idea of marine biodiversity and made us aware of entirely new habitats such as seamounts, mid-oceanic ridges, whale carcasses, hydrothermal vents, and human made debris (Norse 1993; Committee on Biological Diversity in Marine Systems 1995). In recent review by Appeltans et al. (2012) showed that the number of eukaryotic marine species described are -226,000 which area one-third of estimated value.

6.3 How new species are described?

Systematics is the study of biological diversity and of the evolutionary relationships among organisms (Simpson 1961; Mayr 1969; Wilson 1985) and taxonomy is a subdivision of this. Taxonomy comprises three associated activities - “identification (referring a specimen to a previously classified and named group), classification (ordering organisms into groups based on perceived similarities or differences), and nomenclature (naming groups of organisms according to rules developed for the process). Systematics also includes the study of the process of evolution and phytogeny. Taxonomic procedure is the practical process of identifying, recognizing, researching, or redescribing a taxon for scientific publication according to the current rules of biological nomenclature. Biological nomenclature, the system of scientific naming of organisms, was developed to ensure that every organism can have a name that is refers only to that particular kind of organism and globally

Response of Bentfiic community structure to tfie BaBitat Beteropeneity in Indian Ocean 149 I ^ a u c 'Discovery of species Chapter - 6

understood. A species becomes known in the scientific sense when a Latin binomial, a name consisting of two parts (a genus term and a species term), and a description are published in the scientific literature, according to the rules of botanical (The International Code of Botanical Nomenclature, ICBN) or zoological (The International Code of Zoological Nomenclature, ICZN) nomenclature. Although they are written in legal language, there is no agency to enforce these codes; there is only the consensus of biologists to observe and accept them (Jeffrey 1989). Describing new species is still an important part of taxonomy. About a third of all taxonomic papers published over the last 28 years contain a description of at least one new species.” - Judith E. Winston (1999).

Due to the less number of studies carried out in Indian Ocean, the possibility to find of the new organisms are high. There are many habitats remain to explored especially in deep-sea. During the present study some modem techniques have been used to collect sample from few wonderful habitats like seamounts, mid-oceanic ridge, abyssal floor etc. In this chapter, new genus, species of Hexactinnellid sponges and brittle stars from seamount and mid- oceanic ridge are described.

'Response of 6enthic community structure to the habitat heterogeneity in Indian Ocean 150 \tr * » *> Discovery o f species Chapter - 6

6.A Description of a new species oi Hyalascus (Hexactinellida:

Rossellidae) from a volcanic seamount in the Andaman Sea

Hyalascus was established by Ijima in 1896 for a sponge from Sagami Bay (Japan). The genus comprised eight doubtless species until now: H. haculifer (Schulze 1886a); H. stellatus (Schulze 1886b); H. sagamiensis Ijima, 1896; H. giganteus Ijima, 1898; H. similis Ijima, 1904; H. attenuatus Okada, 1932; H. anisoactinus Tabachnick and Levi, 2004; H. pinulohexactinus Tabachnick and Levi, 2004; all occurring in the Pacific Ocean only. Hyalascus hodgsonii Kirkpatrick, 1907 from the Antarctic Ocean appears to be a doubtful representative of the genus due to the presence of two types of microdiscohexasters; one with numerous secondary rays, and another possessing a reduced number of these rays. The transfer of this species to Scyphidium by Tabachnick and Levi (2004) appears reasonable since presence of two types of discoidal microscleres is the diagnostic character for Scyphidium (Tabachnick 2002). The assignment by Koltun (1964) of Hyalascus attenuatus Okada, 1932 to the synonymy of Aulosaccus schulzei Ijima, 1896 was rejected later (Tabachnick 2002). Koltun found two specimens, identified by him as Hyalascus attenuatus, with large spherical discohexasters. As a consequence, these specimens should be regarded as representatives of Aulosaccus Ijima, 1896. In part, Ijima's decision was derived from the observation that hypodermal pentactins were absent in Aulosaccus (cf. Ijima 1904). Nevertheless, Okada (1932) noticed that this trait does not seem to be important, as opposed to the large discohexasters, judged a more reliable diagnostic character for Aulosaccus. Some hypodermal pentactins may be present in the latter. Following this argument, later inadvertently supported by Tabachnick (2002), A. mitsukurii Ijima, 1898 (1904) from Sagami Bay (Japan), was referred to Hyalascus. This was a mistaken decision nevertheless, as this species has two distinct types of

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 1511 P Discovery of species Chapter - 6 discoidal microscleres and should finally be considered a doubtless representative of Scyphidium Schulze, 1900.

Hyalascus is defined as Rossellinae with saccular body and only one type of discoidal microscleres - the smallest ones microdiscohexasters. Dermalia are pentactins and stauractins, hypodermal pentactins (if present) have orthotropal tangential rays (Tabachnick 2002).

Taxonomy

Order Lyssacinosida Zittel, 1877 Family Rossellidae Schulze, 1885 Genus Hyalascusljimn, 1896

Hyalascus andamanensis sp. nov.

Material examined: Volcanic seamount, Andaman Back Arc Basin, Andaman Sea: R.V. ‘SONNE, stn. TVG-9, 25.XI.2007, 7°56.036’ N 94°03.026’ E, 705 m.

Holotype, NIO/BOD /3/2010, stored in alcohol. IORAS il, slide.

Etymology, The species name is derived from its place of collection.

Description, Body: The sponge has a white cylindrical body, about 13 mm long and 6 mm in diameter; the osculum is 4 * 3 mm in diameter, the walls are very thin 0.5 -1 mm . Prostalia lateralia are hypodermal pentactins which protrude at about 300 pm above the dermal surface (Figure 6.A.1).

Spicules (Figure 6.A.2): The choanosomal skeleton is composed of diactins 700 - 3800 pm in length and 4 - 15 pm in diameter; they have rounded, rough outer ends and stout, smooth shafts. Hypodermal pentactins have orthotropal tangential rays about 800 - 1700 pm in length and 8 - 24 pm in diameter, the proximal ray is more than 1400 pm in length. Some of the tangential rays are smooth, the others have rough surface; the outer ends are conically pointed.

‘Response of BentfUc com m unity structure to tfie fiuBitut Heterogeneity in IncCian Ocean 152 | i' a u v Discovery of species Chapter - 6

Dermalia are stauractins, rarely tauactins and pentactins, sometimes they have 1 - 2 rudimental tubercles instead of the reduced rays. The rays of dermal stauractins are rough with rounded or conically pointed outer ends, have 59 - 111 pm in length (n=25, avg=93, std=12) with a diameter of about 5 pm. Atrialia are hexactins, their rays directed inside the atrial cavity are 67-215 pm in length (n=23, avg=161, std=36), tangential rays are 74 - 200 pm in length (n=24, avg=146, std=30), ray directed inside the body is 41 - 207 pm in length (n=22, avg=138, std=36). The rays are 5 - 7 pm in diameter, their surface is rough and outer ends are rounded or conically pointed.

Microscleres are oxyhexactins together with some oxyhemihexasters and oxyhexasters and microdiscohexasters. Oxyhexactins are 67 - 141 pm in diameter (n=25, avg=103, std=3). Oxyhemihexasters and oxyhexasters are 74 - 141 pm in diameter (n=10, avg=98, std=20) with primary rosette 7 -1 0 pm in diameter (in the latter). Microdiscohexasters are spherical, 18 - 25 pm in diameter (n=7, avg=22, std=3) with primary rosette 4 - 7 pm in diameter (n=7, avg=6, std=l).

Remarks: Most species of Hyalascus have dermal spicules predominately in the form of pentactins: H.baculifer, H. giganteus, H. similis and H. stellatus. In one species, they are mostly hexactins: H. sagamiensis. Four species, including the new one, have mostly stauractins: H. Andamanensissp. nov., H. anisoactinus,H. attenuatus and H. pinulohexactinus. The new species differs by the smallest size of microdiscohexasters, 18-25 pm in diameter, while in all other species, these spicules are larger (25 — 72 pm in H. anisoactinus; 25 - 65 pm in H. pinulohexactinus) and even notably larger in some species (about 117 pm in H. baculifer and about 63 pm in H. stellatus). Distribution map of the species found o f the genus Hyalascus in the world ocean showed in Figure 6.A.3.

'R&spon.se of BentBic community structure to tfie haBitat heterogeneity in Indian Ocean 153 M’ * u. t Discovery of species Chapter - 6

Figure 6.A.I. Hyalascus andamanensis sp. nov.: (A) upper part of type specimen with osculum and (B), its’ lateral view showing the basal broken part.

C A-B; D-l J-K VJ

Figure 6.A.2. Hyalascus andamanensis sp.nov., spicules of the holotype. A, dermal stauractin. B, atrial hexactin. C, hypodermal pentactin. D, E, fragments of tangential rays of hypodermal pentactins. F, choanosomal diactin. G, oxyhexactin. H, oxyhemihexaster. I, oxyhexaster. J, K, microdiscohexasters.

Response op Bent Hie community structure to tfie HaBitat Heterogeneity in Indian Ocean 154 | P a g c Discovery of species Chapter - 6

Figure 6.A.3. Map showing the distribution of Hyalascus in the world Oceans. A, H. anisoactinus; B, C, D, H. pinulohexactinus\ E, F, H. attenuatus; G, H. sagamiensis', H, H. similis\ I, H. baculifer, J, H. stellatus\ K, H. andamanensis sp.nov.

■ Response of Sent Hie community structure to the Habitat Heterogeneity in Indian Ocean 1551 P a g e Discovery o f species Chapter - 6

6.B A new genus and species of deep-sea glass sponge (Porifera: Hexactinellida: Aulocalycidae) from the Indian Ocean

The family Aulocalycidae was established by Ijima (1927) for 5 genera (Figure 6.B.1): Aulocalyx Schulze, 1886, Rhabdodicyum Schmidt, 1880, Tretopleura Ijima, 1927, Euryplegma Schulze, 1886 and Fieldingia Kent, 1870. One genus Ijimadyctyum Mehl, 1992 was raised from a previously known second species, Rhabdodicyum kurense Ijima, 1927. One genus was added later Leioplegma Reiswig and Tsurumi, 1996. Tabachnick and Reiswig (2000) ejected two genera: Tretopleura and Fieldingia form the family and a suggested a new order Aulocalycoida with a single reorganized family. A new subfamily Uncinateriinae with two genera: Uncinatera, Topsent, and Tretopleura were suggested by Reiswig (2002) as a subdivision of Aulocalycidae together with Aulocalycinae (with the scope and definition of former Aulocalycidae of Tabachnick and Reiswig (2000)). A new subfamily Cyathellinae of the family Aulocalycidae with the only genus Cyathella Schmidt, 1870 was suggested by Janussen and Reiswig (2003). The new genus, describing in this paper is a unquestionable representative of the family Aulocalycidae sensu Tabachnick and Reiswig (2000) and subfamily Aulocalycinae sensu Reiswig (2002).

Taxonomy Family Aulocalycidae Ijima, 1927

Indiella gen. nov. Diagnosis. Fan (or funnel)-like basiphytous sponge with thin walls and numerous epirhyses. Framework contains several layers of regular dictyonal strands (mainly from the atrial side) and irregular fused hexactinic spicules (which form a typical aulocalycoid skeleton) located among them and from the dermal side. Dermalia and atrialia are pentactins. Microscleres are discohexasters.

'Response o f benthic com munity structure to the habitat heterogeneity in Indian Ocean 156 11> a e Discovery ofsjyecies Chapter - 6

Etymology. The name o f the genus is derived from its place o f collection and refers to the Indian Ocean.

Definition. Aulocalycidae with fan (or funnel)-like body, epirhyses, and several regular layers of dictyonal strands located mainly on the atrial side.

Remarks. It is likely that the body is rather fan-like than cup or funnel-like since the fragments are flat, thus the funnel-like body shape should be of a very large diameter. The original shape of the body is already known in Aulocalycoidae: Leioplegma Reiswig and Tsurumi 1996, while wide funnels are unknown. Basiphytous type of fixation to likely hard substratum is suspected since all other representatives of the family have it. The taxonomic affiliation of genus Cyathella (its attribution to the Aulocalycoida, Aulocalycidae with definition of a new subfamily Cyathellinae was made by Janussen and Reiswig 2003), possessing a rhizophytous type of fixation is unique for recent hexactinellids with rigid skeleton. The walls in the new genus are relatively thick (in comparison with other representatives of the family). Usually the aulocalycoid skeleton is composed of large hexactins located approximately in a single layer, their rays are distributed in a single plane (the distal one and proximal are bent), fusion takes place at points o f mutual contact, so the wall thickness includes an only dictyonal layer. The regular dictional strands are observed in Leioplegma only, they are present as a single layer of parallel units longitudinally distributed, and irregular aulocalycoid skeleton is situated among them (Reiswig andTsurumi 1996). The walls in Euryplegma appear to be very complicated and their construction has no equivalent interpretation (Tabachnick and Reiswig 2000). Cyathella has similar framework construction with several layers of dictyonal strands, but it has no channels and likely no loose spicules. The presence of epirhyses type of channelization is unique for the family. It is known in Euretidae (Hexactinosida), for instance, in Chonelasma (Reiswig

'Response of Benthic community structure to the BaBitat heterogeneity in Indian Ocean 157 J Discovery o f species Chapter - 6 and Wheeler 2002). Among the other types of channelization in Aulocalycoidae, only schizorhyses-like ones are known in Euryplegma, meantime as in the case with complicated wall construction, they may be intercavaedia-like constructions between the atrial cavity and numerous small lateral oscula (Tabachnick and Reiswig 2000). The loose spicules are typical for the family where few species possess scepters and uncinates. A more simplified spicule set is observed in Heterochone (Hexactinosida: Euretidae), which has no loose spicules other then discohexasters (Reiswig and Wheeler 2002). The situation with aulocalycoid, paraulocalycoid and skeleton of Cyathella- like construction (Reiswig 2002; Janussen and Reiswig 2003) is becoming more complicated after finding in the dictional strands of Farrea numerous axial canals (Reiswig and Wheeler 2002), thus the definition of Aulocalycidae into subfamilies seems to be poorly established and the new genus is regarded as a representative of Aulocalycidae.

Type species. Indiella ridgenensis sp.nov.

Indiella ridgenensis sp.nov. (Figs. 2-4;)

Etymology. The species name is derived from its type locality, the ridge

(Carlsberg Ridge) habitat. Material examined. Carlsberg Ridge, Indian Ocean: ‘Akademic Bois Petrov’ station. DR-13, 07°00.466' N, 59°56.295'E, 2589 m, November 2009. Holotype: NIO/BOD/5-H/2011, stored in ethanol. NIO/SPONGE/DR-13/H, slide, stored in ethanol. IORAS (Institute of Oceanology of RussianAcademy of Sciences) 5/2/ NIO/BOD/5-H/2011 (slides). Paratypes: NIO/BOD/5-P1, NIO/BOD/5-P2, NIO/BOD/5-P3, stored in ethanol. NIO/SPONGE/DR-13/Pi, NIO/SPONGE/DR-13/Pii, NIO/SPONGE/DR-13/Piii, slides. TOP AS NIO/BOD/5-P1, NIO/BOD/5-P2,

NIO/BOD/5-P3, slides.

‘Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 158 | r u a c Discovery of species Chapter - 6

Description. Body: The sponge consists of small, lamellate, thin fragments. The holotype is a flat fragment approximately 40x17 mm about 1 mm in thickness (Figure.6.B. 2i). Paratypes are similar: Pi is a lamellum 20x25 mm (Figure.6.B.2ii); Pii is 30x20 mm (Figure.6.B.2iii); Piii is 50x45 mm (Figure.6.B.2iv). From the dermal side numerous epirhyses are observed, they are 1.3 - 1.5 mm (Figure.6.B.4C) in diameter and penetrate about a half of the wall thickness. Spicules framework is seems to be constructed of different elements: regular, longitudinally directed dictyonal strands, located mostly in the vicinity of the atrial surface (approximately 4 layers) and irregular hexactins fused to each other and to the regular elements at points of mutual contacts, at all levels of the wall thickness. All framework surfaces are covered by very small spines, the free outer ray ends are conically pointed. The dictyonal strands are easily observed, they have diameter 0.09-0.12 mm, beams between the strands are 0.03-0.07 mm in diameter. Free rays of the dictyonal strands are protruded atrially. The meshes between the dictyonal strands and their connecting beams are rather regular, usually rectangular, 0.3-0.5x0.5-0.8 mm. Adjacent hexactinic spicules located among the dictyonal strands are irregularly and sparsely distributed among their meshes, they are connected to the framework by a single ray (small hexactins with rays 0.07-0.12/0.003-0.006 mm) and often at points of mutual contact (large hexactins with rays about 0.5/0.012- 0.018 mm). The meshes there are very irregular and of different sizes. The dictyonal strands may be also observed in the vicinity of dermal surface but due to numerous epirhyzes, they are not straight as those from the atrial

surface.

Loose spicules: dermal and atrial pentactins are similar to each other, they always have a rudiment about 0.02 mm long instead of the ray directed outside the body, rough surface, their outer ends are clavate, rounded, lanceolate or sometimes conically pointed. Tangential rays of dermal pentactins are 0.102-0.432 mm long (Table 1), the ray directed inside the body

'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 159 | V a g «* Discovery of species Chapter - 6

is 0.048-0.258 mm long (Table 1), the diameter of these rays is 0.002-0.009 mm. Tangential rays of atrial pentactins are 0.078-0.372 mm long, ray directed inside the body is 0.036-0.342 mm long (Table 1), the diameter of these rays is 0.004-0.009 mm.

Microscleres are stellate discohexasters only, with 8-14 secondary rays. The diameter of the discohexaster is 0.025-0.046 mm, their primary rosette is 0.006-0.018 mm in diameter (Table 6.B.1).

Remarks. Since all these fragments of the holotype and of paratypes were collected from the same station, there is a great probability that they belong to a single specimen.

Key to the Genera of Aulocalycidae

1. Dictyonal strands not obvious, likely entirely absent (if present they are distributed chaotically), choanosomal hexactins fuse at points of mutual contacts, their distal and proximal rays are bent in the tangential plane (aulocalycoid skeleton)...... 2 Dictyonal strands present in addition to aulocalycoid skeleton , dictyonal strands are distributed in common, longitudinal direction ...... 5 2. Body of branching tubes or cup with short lateral tubes...... 3 Body fan- or tongue-shape without tubular elements..... Euryplegma 3. With rhopalasters as distinctive microscleres...... Aulocalyx Without rhopalasters...... 4 4. Parietal gaps large and closely spaced; wall lace-like...Rhabdodictyum

Response of Benthic community structure to the haBitat heterogeneity in Indian Ocean 16011’ a ^ e 'Discovery of species Chapter - 6

Parietal gaps small, sparse; wall thin and mostly imperforate

...... Ijimadictyum 5* Walls unchannellzed...... L&ioplctgtrici Walls channelized by epirhyses...... Indiella. gen.nov

Remarks. It is not obvious that the genus Euryplegma has schizorhyses, as postulated in the key of genera by Reiswig (2002); a possibility of lateral oscula and cavaedia (Tabachnick and Reiswig 2000) cannot be rejected. This newly suggested version of the key to genera of Aulocalycoidae family avoids this problem.

Table 6.1. Spicule dimensions of Indiella gen. n. ridgenensis sp.n. (in mm).

L - length, D - diameter, d - diameter of a primary rosette (N = number of observations; Min = minimum; Max = maximum; Avg = average; SD = standard diviations). Bold measurements are used in the text sections.

Type L Dermal pentactin L Atrial pentactin Discohexaster

T a n g e n tia l R ay T a n g e n tia l R ay D d ray d irected ray directed discohexaster discohexaster insid e inside body body

N 25.000 25.000 25.000 25.000 28.000 28.000

Min 0 .1 0 2 0.060 0 .0 7 8 0.042 0.0 2 5 0.006

Max 0 .4 3 2 0.258 0.360 0.342 0.0 4 6 0.018

Holotype Avg 0.280 0.103 0.228 0.100 0.039 0.012

SD 0.099 0.048 0.081 0.067 0.005 0.003

N 16.000 16.000 12.000 12.000 14.000 14.000

Min 0.168 0.048 0.108 0.060 0.032 0.009

Response of Benthic community structure to the hahitat heterogeneity in Indian Ocean 161| Discovery of species Chapter - 6

Max 0.408 0.180 0.360 0.156 0.042 0.018

Paratype- Avg 0.256 0.113 0.264 0.115 0.037 0.012 1 SD 0.070 0.049 0.076 0.032 0.003 0.002

N 7.000 7.000 6.000 6.000 3.000 3.000

Min 0.240 0.078 0.132 0.048 0.039 0.012

Max 0.414 0.192 0 .3 7 2 0.114 0.041 0.014

Paratype- Avg 0.348 0.127 0.241 0.075 0.040 0.013 2 SD 0.060 0.039 0.095 0.023 0.001 0.001

N 5.000 5.000 4.000 4.000 1.000 1.000

Min 0.168 0.072 0.150 0.036 0.032 0.008

Max 0.312 0.168 0.240 0.084 0.032 0.008

Paratype- Avg 0.252 0.110 0.197 0.066 0.032 0.008 3 SD 0.067 0.037 0.038 0.021 "

'Response of Benthic community structure to the BaBitat heterogeneity in Indian Ocean 162 11' a t> t- Discovery of sptecies Chapter - 6

0 120 10000 km

Figure 6.B.I. Global distribution of Aulocalycidae including the present study.

A :Aulocalyx irregularis', B: Aulocalyx serialis; C-F: Rhabdodictyon delicatum; G:

Ijimadyctyum kurense; H: Leioplegmapolyphyllon; I-Y : Euriplegma aariculare; Z:

Indiella gen.nov. ridgenensis sp.nov.

Figure 6.B.2. Indiella gen .n ov. ridgenensis sp.nov. (A) view from the dermal side,

(B) view from the atrial side; (i) holotype, (ii) to (iv) paratypes

■ Response of benthic community structure to the habitat heterogeneity in Indian Ocean 163 11> » g t Discovery of sjoecies Chapter - 6

Figure 6.B.3. Scaning Electron M icroscopy of Indeilla gen n. ridgenensis sp.n. Frameowrk and spicules of the holotypes. (A) dermal layer, (B) atrial layer, (C) lateral view, (D) discohexaster, (E) secondary ray tuft of discohexaster

Figure 6.B.4. Indeilla gen n. ridgenensis sp.n. drawings of spicules of the holotypes. (A) dermal pentactin (B) atrial pentactin, (C) discohexaster, (D) secondary ray of discohexaster

'Response, of Benthic community structure to the habitat heterogeneity in IncCian Ocean. 164 (Page Discovery of species Chapter - 6

6.C Bridle stars (Echmodermata: Ophiuroidea) from seamounts in the Andaman Sea (Indian Ocean) - a first account, with descriptions of new

species

The brittle star fauna of the Indian Ocean is less well known than that of the North Atlantic (Mortensen 1933; Paterson 1985; Stohr and Segonzac 2005) or eastern Pacific (O Hara and Stohr 2006) and the knowledge on the ophiuroid fauna in Indian waters is limited. Early accounts of Indian echinoderms were published by Bell (1887). Cruises on the Indian vessel "Investigator" contributed some more material in the late 19th century (Koehler 1899), but progress was slow. James (1970a; 1970b; 1981; 1982a; 1982b) reported on shallow water species in Indian coastal waters, particularly the Andaman and Nicobar Islands, but records of Indian deep water species are scarce. He also provided a review on the status of knowledge on Indian echinoderms (James 1983) to which not much has been added since.

Recent studies on Indian Ocean ophiuroids have focussed on the area around the Mascarene archipelago in the tropical eastern Indian Ocean (Guide and Ribes 1981; Guide and Vadon 1986; Vadon 1991; Guide and Vadon 1985; Rowe and Richmond 2004; Stohr et al., 2008). An inventory of shadow water echinoderms of the Indo-West Pacific was compiled by Clark and Rowe (1971) thirty years ago and it is still the standard reference work on the subject. A recent census counted 319 species of ophiuroid for the Indian Ocean (Stohr et al., 2012), about a quarter of them endemic to the region. By comparison, the same study found 831 species for the Indo-Pacific. This numerical difference may however reflect differences in collecting effort rather than actual differences in species richness.

Seamounts are submarine mountains, often of volcanic origin, elevated from the deep sea floor. Initially, they were thought to be centres of endemism

'Response o f Benthic com munity structure to the habitat heterogeneity in Indian Ocean ,65 | P . 8( Discovery of species Chapter - 6 and high species richness, due to their isolated position (McClain 2007). For ophiuroids however, O'Hara (2007) found no elevated levels of endemism or species richness on seamounts in general, although individual seamounts may vary greatly from each other in faunal composition. In general, seamounts reflect the fauna of the surrounding deep sea floor. For the purposes of biological inventories, seamounts are more accessible to observation and collecting than the deep-sea floor. Particularly, rare species of the deep sea with limited geographical distribution and/or low densities may go unnoticed for a long time, despite centuries of ocean exploration. Ophiuroids are a dominant component of the deep-sea benthic fauna (Gage and Tyler 1991). Yet, until now, none have been recorded from Indian water seamounts, according to the Seamount Online database (http://seamounts.sdsc.edu).

A multidisciplinary research programme has been initiated by Indian researchers to explore the Andaman Back-arc Basin (ABB), including seamounts. The ABB is an active marginal basin and a part of the major island arc-trench system in the northeastern Indian Ocean. It marks the eastern boundary of the Indian plate where it sub-ducts beneath the Southeast Asian plate. The German research vessel "Sonne" was used to sample and collect geophysical, geological, chemical and biological data from the Andaman seamounts in 2007. Two seamounts were studied during this cruise, the crater seamount (CSM), which is a submarine volcano with conical shape, discovered recently (Kattoju et al., 2010), and a second seamount (SM2), non- volcanic, with flat top.

This is the first time report on the ophiuroid species collected on these two seamounts. Two species are new to science and will be described below.

Response of Bent file community structure to tBe BaBitat heterogeneity in Indian Ocean 166 | f * *4 •Discovery of species Chapter - 6

Material and methods

Rocks and their attached and associated fauna were collected at various depths on two seamounts (CSM and SM 2) in the Andaman Sea, Indian Ocean, using a Television Gripper (TVG), in October-December 2007 (Please see the locations map in Figure 4.1 Chapter 4). A total of four TVG transects were executed, TV9 and TVG10 on the CSM and TVG11 and TVG 12 on SM2, and four samples were collected. Brittle stars were found in the samples from TVG 9, 10 and 11, attached to the rocks. They were carefully picked off and preserved in 70% ethanol. For a more detailed description of methods and general results please see Chapter 4.

The holotypes of each new species were lightly bleached with diluted household bleach (NaOCL:water, 1:1) for about 20 seconds, to clean their surface. They were extremely brittle and easily lost scales and papillae, which prohibited stronger treatment. The specimens were mounted on aluminium stubs with non-permanent spray glue, gold coated and examined with a Hitachi FE-SEM scanning electron microscope (SEM). Then the specimens were removed from the stub by resolving the glue with butyl acetate and brushing with a small artist brush, re-attached with fresh glue, opposite side exposed, and examined in the SEM again. Arm fragments were dissociated in undiluted bleach to isolate the ossicles. These were then washed with tap water and mounted wet on stubs coated with spray glue. Measurements of whole specimens where taken with an ocular micrometer on a dissecting microscope, smaller structures were measured with the SEM scale. All material has been deposited at the Swedish Museum of Natural History.

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 16711’ » g t Discovery o f species Chapter - 6

Taxonomy

Family Ophiuridae Muller and Troschel, 1840

Subfamily Ophioleucinae Matsumoto, 1915

G enus Ophioleuce Koehler, 1904

Type species. Ophioleuce seminudum Koehler, 1904

Diagnosis. Based on the type species the following features characterize the genus Ophioleuce and consequently the subfamily Ophioleucinae. Disk round, with sharp edge, notched at arm bases, more or less fully covered with granules, sometimes intermingled with slender spines. Arms inserted ventral to the disk. Second tentacle pore inside mouth slit, covered by one or several scales. Arm plates weakly striated; spine articulations u-shaped with pronounced rim. Long adoral shields, separating oral shield from first ventral arm plate.

Remarks. Over time, several species that deviate somewhat from the above diagnosis have been included in Ophioleuce. Madsen (1983) stressed the importance of the position of the second tentacle scale hidden inside the mouth slit and covered by large scales as important for the delimitation of Ophioleucinae from Ophiurinae, in which the pore is somewhat removed from the mouth slit and surrounded by small scales. However, in O. oxycraspedon Baranova, 1955, O. gracilis Belyaev and Litvinova, 1976 and O. depressum (Lyman, 1869) the second pore is slightly superficial, surrounded by several small scales. Also, O. gracilis and the Atlantic species identified as O. oxycraspedon by Paterson (1985) have a sparse disk granulation, forming a net-like pattern. The type of the Pacific O. oxycraspedon had a denser granulation, leaving only the radial shields and some marginal plates bare (Dyakonov, 1954; Baranova, 1955), which suggests that the Atlantic record needs to be re-evaluated. In O. oxycraspedon and O. gracilis, the disk edge bears a fringe of small papillae that are likely homologous to granules. A

'Response of Benthic community stnuctuve to the habitat hetevogeneity in Incfiun Ocean 168 | P a 5* e Discovery of species Chapter - 6 revision of the Ophioieucinae is necessary to better understand the phylogenetic value o f these characters, but outside the scope of this study.

Ophioleuce longispirtum new species (Figures 6.C.1- 2)

Material. Holotype, on SEM stub; TVG 9, Andaman Sea, Andaman Back- Arc basin, crater seamount (CSM), flank, 07°55.924'N, 94°03.139'E to 07°56.036'N, 94°03.026'E, 517-671 m, 25/11/2007 [SMNH-Type-8199]; arm fragments on SEM stub, unknown from which specimen(s), same sample [SMNH-Type-8200]; skeletal elements on SEM stub from detached arm fragment, same sample [SMNH-Type-8201]; 4 paratypes, same sample, in 80% ethanol [SMNH-Type-8202]; 1 paratype, in 80% ethanol, TVG 10, Andaman Sea, Andaman Back-Arc basin, CSM, summit, 07o56.3330rN, 94°02.638'E to 07°56.255'N, 94°02.693’E, 373-394 m, 26/11/2007 [SMNH- Type-8203],

Etymology. The specific name alludes to the long dorsal spines on the first arm segment.

Diagnosis. Species of Ophioleuce with two long, rod-like spines on the dorsal portion of the first lateral arm plates. Up to 18 fringe spines in each interradius. Second tentacle pore slit-shaped, opening into the mouth slit, bordered by several low scales. No other tentacle scales along arm. Large round ventral spine articulation with thickened rim opening ventrally, smaller u-shaped articulation dorsal to the first, opening dorsalwards. Dorsal disk scales with borders of low round granules.

Description of holotype. Disk round, slightly domed, thin, 5.2 mm dd, weakly incised at arm base. Arms broken close to the disk, but fragments in the sample suggest long, carinate, tapered, whip-like arms, at least 5 times dd long. Disk scaling formed by primary rosette of more or less round single central plate and five radial plates in disk centre, a circle of three smaller

'Response of Benthic community structure to the hahitat heterogeneity in Indian Ocean 1691 Is ^ r e Discovery of species Chapter - 6 triangular interradial plates and a larger rhombic radial plate, separating radial shields proximally. Interradially between radial shields, a series of three plates, two rectangular plates, overlapping, wider than long, proximally a large distal one, triangular with obtuse proximal angle, as long as distal width, overlapping second plate. Radial shields about half as long as disk radius, triangular, with wider outer edge, completely separated by a series of plates, a large rhombic proximal plate, a narrower elongated plate, a small round scale, and a short, wide distal scale with depressed distal half. Each radial shield separated from arm by a wide plate, three times as wide as long. These and the last scale separating the radial shields form a trio of plates on the arm base. Disk edge with fringe of 18 elongated scales per interradius. All disk plates with open meshwork stereom, bearing low conical granules along their edges.

Dorsal arm plates contiguous, rectangular, longer than wide, with straight edges, laterally overlapped by convex lateral plates. Lateral and dorsal arm plates striated. Each lateral arm plate with single, flat, triangular spine, standing erect off arm, parallel to disk edge, decreasing in size, becoming increasingly rod-like distalwards along arm; edges finely serrated, stereom multi-layered mesh. Single large, round u-shaped spine articulation with thickened rim of smooth, entire stereom, enlarged smooth distalwards directed lip, opening distalwards, and single central muscle opening, on proximal segments; nerve opening not obvious or reduced. Distalwards a second lateral spine appears, dorsal to the first, rod-like. Dorsal articulation half as large as ventral one, opening dorsalwards. On each first arm segment a long rod shaped spine on upper part of each lateral plate, laying diagonally across radial shields, most of them broken, but intact spines more than 1 mm long. Long spine articulation strongly reduced, consisting of larger muscle opening and smaller nerve opening with low rim.

Ventral disk formed by large, quadrangular to pentagonal scales. Jaws with pointed triangular apical papilla (presumably first tooth). Oval, bowl shaped dental plate with long pointed tooth at dorsalmost part, widely

Response of Bent file community structure to tBe BaBitat Beterogeneity in Indian Ocean 170 | P a ** <• Discovery of sjtecies Chapter - 6 separated from apical papilla/tooth. 7 block-like papillae in a series from tip of jaw to distal end of second, slit-shaped, tentacle pore, which opens into mouth slit. Oral plates of each jaw positioned at an angle, v-shaped. Adoral shields narrow, bordering proximal edges of oral shield, extending along first ventral arm plate, bordering proximal part of bursal slit. Oral shields triangular with wide proximal angle, distal edge convex. Madreporite distinguished by distinct hydropore, eccentric at distal edge. Bursal slit does not reach disk each, as long as first two arm segments, edge of long narrow abradial genital scale and lateral plates bordering bursal slit, minutely thorny. Ventral arm plates t-shaped with wavy distal edge, strongly concave lateral edges. First ventral plate bent upwards into mouth slit, distally contiguous with second plate, from 5th segment ventral plates widely separated by lateral plates. Lateral arm plates with sharp angle, separating lateral and ventral surface of plate, ventrally concave. Tentacle pores large, round, lacking scales. On first segment of each arm a pair of smaller holes of unknown function in proximal ventral surface of lateral arm plates. Fringe spines ventrally concave, proximal ends depressed, attached to depressions in disk edge.

Internal characters. Arm skeleton dissociated from arm fragments not assignable to a particular specimen. Vertebrae elongated, with zygospondylous articulation, large wing-like muscle flanges distally and proximally. Ventrally, vertebra with two median flat processes, to which lateral plates attach. Lateral plates with corresponding internal process. Dorsal plates convex, lateral edges slightly concave, stereom with many larger holes and transverse striations. Ventral plates convex, with upwards bent distal part, stereom with few small holes, smooth.

Paratype variations. In the same sample as the holotype (TVG 9) there were an additional four specimens with disk diameters 2.3, 4.2, 4.5 and 4.6 mm. Another specimen of 5.3 mm dd was found in sample TVG 10. All specimens are more or less covered in a layer of fine sediment or organic matter embedded in slime, which firmly glues the long spines to the disk in preserved

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 17111* » i- Discovery ofsjyecies Chapter - 6 animals. All arms are broken, but arm fragments are included in the samples. On all individuals, the disk fringes are damaged, many of the spines lost. Complete interradial fringes consist of 17-18 spines in the larger specimens, 12 in the smallest one. Specimens of 4.5 mm dd and above have seven lateral oral papillae, the 4.2 mm dd specimens has six and the 2.3 mm dd specimen five papillae. The long upper first disk spines are mostly broken or lost, but fragments and single intact spines show that all of these specimens originally possessed these long spines. Large gonads are visible inside the translucent disk, next to the arms, in all but the smallest specimen.

Remarks. In O. longispinum sp. nov. the second tentacle pore is close to the mouth angle, slit-like narrow and opens into the mouth slit. It is also bordered by low scales and overall resembles the condition found in Ophiura, thus suggesting a placement in Ophiuridae. Although this character suggests a placement in the subfamily Ophiurinae, I propose to place it in Ophioleucinae, because all other characters agree with that subfamily. In addition, the superficial placement of the second pore is a juvenile character (Sumida et al., 1998; Stohr 2005) and its value for classification above genus level is questionable. At first glance, this new species is similar to Ophiophyllum, with its limpet-like, fringed disk, paddle-like modified lower arm spine, carinate, ventrally concave arms, lateral arm plates with a sharp lower edge and broad ventral surface, and the large tentacle pores. However, the granulated dorsal disk, block-like oral papillae, striated arm plates, slit-like second tentacle pore surrounded by scales, and the rectangular dorsal arm plates are characters shared with Ophioleuce. The critical clue revealing the close affinity of O. longispinum sp. nov. with Ophioleuce is found in the arm spine articulation. Martynov (2010) argued that the spine articulation reflects phylogenetic relationships between ophiuroid families. The articulation of O. longispinum sp. nov. is similar to that shown for several Ophioleucinae (Martynov 2010) and to that of Ophioleuce seminudum, the generic type, and O. gracilis Belyaev and Litvinova, 1976 (Martynov, personal communication). Although some similarity between the articulations of Ophioleuce and some species of

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 172 | !• a s f Discovery o f species Chapter - 6

Ophiophyllum can be observed (see below), they are clearly different and O. longispinum has a typical ophioleucin articulation. Another strikingly conservative feature appears to be the rectangular shape of the dorsal arm plates in all species of Ophioleuce, but no species of Ophiophyllum.

The large open tentacle pores lacking scales, the more developed but still superficial first pore, the sparse granulation of the disk, the bowl-shaped dental plate bearing few teeth, the along most of the arm widely separated ventral arm plates and the low number of spines are all indications of a juvenile, paedomorphic state that may have evolved independently in both genera. The limpet-like shape of the disk, the disk fringe and the modified lower spine may be ecological adaptations, or they may indicate phylogenetic relationships. It is possible that the genus Ophiophyllum evolved from the paedomorphic branch of Ophioleuce, but a thorough evaluation of all species of both genera is needed to answer this question. A phylogenetic analysis of these genera is beyond the scope o f this paper, but will be explored in a future study.

Ophioleuce longispinum sp. nov. differs from all known congeners in the presence of long dorsal arm spines on the first segment and in the shape of the lower arm spine. It is closest to O. oxycraspedon and O. gracilis, both of which share the flat, sparsely granulated disk and edge fringe, but they do not have the strongly modified lower arm spine and their fringe consists of shorter papillae.

Distribution. According to type localities and GBIF records, of the seven species of Ophioleuce, O. depressum isrestricted to the Atlantic Ocean, where also O. oxycraspedon has been found, although records of the latter need to be verified. Ophioleuce longispinum sp. nov. and O. seminudum are known from the Indian Ocean, while O. regulare (Koehler 1900) is a species of the Southern Ocean and O. oxycraspedon has been described from the Bering Sea. Ophioleuce gracilis, O. brevispinum (H.L. Clark, 1911) and O. seminudum occur in the Pacific Ocean. Most of the species, including O.

■ Response of Bent Hie community structure to the habitat heterogeneity in Indian Ocean 173 11> * s Discovery of species Chapter - 6 longispinum sp. nov., have been found at depths of few hundred to about 1000 m, whereas O. oxycraspedon and (). gracilis are bathyal species at 2000- 3000 m.

Taxonomy

Subfamily Ophiurinae Lyman, 1865

Genus Ophiophyllum Lyman, 1878

Type species. Ophiophyllum petilum Lyman, 1878: 130, pi. VII figs 179-181.

Diagnosis. A genus of Ophiurinae with round, flat, thin disk, slightly limpet- like domed; long, carinate, ventrally concave arms. A fringe of short, flat spines along interradial disk edge. Three arm segments included in the disk (in adult specimens). Two arm spines, ventral spine more or less transformed, scale or paddle-like, dorsal spine small, pointed.

Ophiophyllum m inim um sp.nov. (Figures 6.C.3, 4)

Material. Holotype, on SEM stub, TVG 9, Andaman Sea, Andaman Back- Arc basin, crater seamount (CSM), flank, 07°55.924'N, 94°03.139'E to 07°56.036rN, 94°03.026’E, 517-671 m, 25/11/2007 [SMNH-Type-8204]; 2 paratypes from same sample, in 80% ethanol [SMNH-Type-8205].

Comparative material. Ophiophyllum novaecaledoniae Vadon, 1991, holotype, New Caledonia, sta. CP 72, 2100 m [MNHN Ec Os 22134], Ophiophyllum borbonicum Vadon and Guille, 1984, holotype, Reunion Island, MD 32, stn DC64, 21°12'S, 55°05'E, 1150-1180 m [MNHN Ec Os 22064],

Etymology. The specific name alludes to the small size of this species, the smallest of the genus.

■ Response of benthic community structure to the habitat heterogeneity in Indian Ocean 1741 i» „ « ,• Discovery of species Chapter - 6

Diagnosis. Species of Ophiophyllum with large, flat disk scales, 14-15 fringe spines in each interradius, large rectangular ventral disk plates, lacking tentacle scales. Largest known size 2.5 mm dd.

Description of holotype. Disk round, slightly domed, 2.5 mm dd. Arms carinated, all broken. Dorsal disk with large round central plate, surrounded by a circle of smaller overlapping scales, then a circle of five larger plates (presumably the radial primaries), separated by smaller scales. Radial shields triangular, half the disk radius long, completely separated by a distal wedge- shaped plate and smaller proximal scales. In each interradius a rectangular distal plate, twice as along as wide and a short quadrangular plate, proximally overlapped by other scales. All scales and plates with finely porous stereom. In each interradius a fringe of 13-14 rectangular spines with straight distal edge and porous stereom, inserted under the dorsal disk plates in a groove running along the edge, hiding about half their length. Fringe spines closest to arms triangular, larger than remaining, block-like rectangular spines. Dorsal arm plates triangular, slightly longer than wide, contiguous, bordered by the larger lateral plates. A tiny first dorsal arm plate inserted between radial shields distally. A large leaf-shaped ventral spine and a much smaller conically pointed spine dorsal of it on each lateral arm plate. Lateral plates and leaf-spines strongly striated.

Ventral disk formed by 3 rectangular, slightly flaring distal plates, 2 narrow abradial genital plates and up to 3 round proximal scales, variable between interradii. Oral shields wider than long with obtuse proximal angle and strongly convex distal edge. Madreporite not distinguishable. Jaws with large round distal scale, middle low wide buccal scale, on some jaws fragmented into smaller papillae, apical papilla and tooth fallen off, conical, sharply pointed. Round, bowl-shaped dental plate with two tooth articulations. Oral plates curved. Adoral shields long and narrow, bordering proximal angle of oral shield, extending past second tentacle scale to bursal slit. Bursal slit as

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 175 | !• „ i> r Discovery of species Cfiapter - 6 long as first two segments, edges smooth. Second tentacle pore large, round, lacking scales, separated from mouth slit by first ventral arm plate.

Lateral arm plates with sharp lateral edge, forming an angle between lateral and ventral surface, outwards flaring, giving ventral arm wing-like appearance. Ventral stereom of lateral plate smooth and entire, with series of holes that demarcates outer wing-like part. Ventral arm plates contiguous, elongated pentagonal with truncated proximal angle, strongly excavated lateral edges in lower half of plate. All tentacle scales similar to first, large, round, lacking scales. Spine articulations vertical at distal edge of lateral plate, inserted under the lamellar stereom of the plate, opening distalwards.

Internal characters. Arm skeleton dissociated from fragment not assignable to a particular specimen. Vertebrae with zygospondylous articulation, elongated, in proximal arm shorter and wider, in distal arm longer and incompletely fused; with two processes in middle of ventral side to which corresponding processes of lateral plates attach. Inside of lateral arm plate with process, stereom on lateral surface lamellar striated; proximal edge concave, distal dorsal edge convex. Spine articulations restricted to ventral part of lateral surface o f plate, inserted at the edge of the plate, partly overlaid by the plate edge, round openings with lower lip. Ventral arm plate stereom dense, with small pores. Dorsal arm plates ventrally concave, dorsally convex, stereom with larger pores, dorsal side with short thorns, rough.

Paratype variations. A paratype of 2.1 mm dd has 15 fringe spines. A second paratype of 1.3 mm dd, with a hole in the centre of its dorsal disk, has 12 fringe spines and shorter arms; its jaws are damaged. Several arm fragments are also included in the sample, but cannot with certainty be matched to a

specimen.

Remarks. Until now, the genus Ophiophyllum included eight species (Stohr and O’Hara, 2007). Originally, the genus was placed in the family Ophiolepididae, but Vadon and Guille (1984) transferred it to Ophiuridae after

'Response of benthic community structure to the haBitat heterogeneity in Indian Ocean 1761 p a t* e Discovery of species Chapter - 6 examining the holotype of the generic type species 0 . petilum Lyman, 1878, on the grounds o f its second tentacle pore being outside the mouth slit, contrary to Lyman's (1878) original illustration. Stohr and Segonzac (2005) followed this decision, but McKnight (2003) considered his 0. teplium McKnight, 2003 within Ophiolepididae, as did Martynov and Litvinova (2008) with their new species 0. nesisi Martynov and Litvinova (2008), but neither of these authors gave an explanation. This question needs to be revisited here to eliminate the resulting confusion. In Ophiolepididae, the second tentacle pore is completely hidden inside the mouth slit, covered by the distal oral papilla, whereas species with the second pore placed outside the mouth slit, bordered by several scales or papillae, are usually assigned to Ophiuridae, mainly the subfamily Ophiurinae (but for exceptions see above). Ophiophyllum is characterized by a large round second tentacle pore, placed at a distance from the mouth angle, thus not in accordance with Ophiolepididae. The position of the second tentacle pore outside the mouth slit is a juvenile character (Sumida et al., 1998; Stohr 2005) and thus doubtful for family delimitation, but pending a revision of Ophiuridae and Ophiolepididae, it seems best not to cause confusion by deviating from this principle. Also, the possible close affinity of Ophiophyllum with Ophioleuce (see above) suggests that both should be included in the same family.

A single species of Ophiophyllum was previously known from the Indian Ocean, at La Reunion, O. borbonicum Vadon and Guille, 1984 (erroneously named O. borbonica, neglecting that phyllum is neuter). Ophiophyllum minimum sp. nov. somewhat resembles O. borbonicum with regard to the pattern of the dorsal disk scalation, but differs in having more fringe scales (O. borbonicum has 9 square spines), different ventral scalation and in lacking tentacle scales (0. borbonicum has two). The number of fringe spines in each interradius has been used to distinguish the species (Vadon and Guille 1984; McKnight 2003). For 0 . atlanticum this was not included in the description, but re-examination of the type images resulted in a maximum of 14 fringe spines and its spine articulations are somewhat similar to the new

Response of Bent file community structure to tfie BaBitat Beterofjeneity in Indian Ocean 1 1 1 | Is a % e Discovery of species Chapter - 6 species. It differs from O. minimum sp. nov. in the dorsal and ventral disk scalation, oral papillae, shape of fringe spines, and shape of ventral arm plates. The other Atlantic species O.nesisi has 12-15 (holotype) and 11-15 (paratype) fringe spines (Martynov personal communication), but differs in having many small tumid dorsal disk scales, a different spine articulation and spines, and rounded fringe spines with entire, smooth stereom. Ophiophyllum novaecaledoniae Vadon, 1991 from New Caledonia differs from O. minimum sp. nov. in having small domed dorsal disk scales among which the primaries are larger, 10 short fringe spines, tumid dorsal arm plates, more and smaller ventral disc scales and a reduced bursal slit. The new species differs from the South Pacific O. petilum in having fewer and larger dorsal disk scales, two dorsal interradial plates, more fringe spines at a smaller disk diameter, fewer ventral interradial plates and different oral papillae. The North Pacific O.concinnus Litvinova, 1981 has more and smaller dorsal disk scales, 7-9 fringe spines, more oral papillae, a longer than wide oral shield and a higher number of ventral disk scales (Litvinova 1981). Ophiophyllum teplium from New Zealand also has more disk scales that are tumid, many more oral papillae and a different ventral disk. Ophiophyllum marginatum A.H. Clark, 1916 from Galapagos has up to 10 fringe spines, up to a dozen ventral interradial scales, longer bursal slits, two tentacle scales and more oral papillae (A.H. Clark 1916).

This is the smallest species o f the genus, although its maximum size may not be known. It shows several juvenile characters (Sumida et al., 1998; Stohr 2005): the curved jaws, few oral papillae and teeth, cupped dental plate, long vertebrae, large tentacle pores lacking scales, second tentacle pore far from mouth slit, but also adult characters such as contiguous dorsal and ventral arm plates throughout the arm, large radial shields, wider than long oral shields, primary dorsal plates separated by scales. The possible affinities of Ophiophyllum with Ophioleuce are discussed above under O. longispinum. Ophiophyllum minimum sp. nov. appears to be less paedomorphic than Ophioleuce longispinum sp. nov., with contiguous arm plates and

-Response of Benthic community structure to the habitat heteroyeneity in Indian Ocean 178 11* a g * Discovery of species Chapter - 6 comparatively less elongated arm segments. The homologies of the fringe spines are not easily deduced in Ophiophyllum, but it is possible that they originated from granules, although no known species has disk granules. They are more specialised than in Ophioleuce, varying in size and shape between larger triangular spines close to the arm and rectangular ones in between. They are also placed in a groove at the disk edge, supported by a ledge formed by the ventral disk plates, whereas the shorter fringe spines/papillae in Ophioleuce longispinum sp. nov. are articulated to small depressions, similar to those found under the disk granules.

Distribution. The genus Ophiophyllum with now nine species has a worldwide distribution, but each species seems to have a narrow range, rarely found outside their type locality. Ophiophyllum petilum was described from the Kermadec Islands (New Zealand) from a sample taken at 390-1119 m, and found later in the North Pacific (GBIF record: SDSC SeamountsOnline 14134). The identity of another specimen from the Caribbean tentatively assigned to that species by Lyman (1883) is doubtful considering the great geographic distance, and its presence there has never been confirmed. The other Atlantic species are so far known only from their type localities, O. nesisi from the Reykjanes Ridge near Iceland at 1670-1895 m depth, O. atlanticum from the axial valley of the mid-Atlantic Ridge at 4078 m, which is the deepest distribution of any of these species. Ophiophyllum borbonicum is known from its type locality at Reunion Island at 1150-1180 m. Among the Pacific species, O. marginatum is known only from Galapagos, found at 717 m depth, O. concinnus from NE of the Mariana Islands was found at 1900 m, and O. novaecaledoniae has the widest depth distribution range with 410- 2100 m. Like O. minimum sp. nov., O. teplium was found on a seamount, north of the Chatham Rise (New Zealand), at 1040-1035 m. Most of these species are known from few or single specimens, only the type series of O. novaecaledoniae consists of 29 specimens of different sizes, including juveniles. Ophiophyllu mminimum sp. nov. is the first record of the genus from Indian waters and the Andaman Sea.

•Response of benthic community structure to the habitat heterogeneity in Indian Ocean 179 | f» * .4 * Discovery of species Chapter - 6

Genus Astrophiura Sladen, 1879

Type species .Astrophiura permira Sladen, 1879: 11.

Diagnosis. Genus o f Ophiurinae with large, thin, pentagonal disk, limpet-like arched, dorsally convex, ventrally concave; thin, short, ventrally concave arms. Six or more arm segments included in the disk (in adult specimens), their lateral plates fused to form most of the distal disk portion beyond the radial shields. Interradial disk edge with fringe of short flat spines. Oral shields reduced except madreporite. Tentacle pores disproportionately large.

Astrophiura cf. tiki Litvinova and Sm irnov, 1981 (Figure 6.C.5)

Material. 1 specimen, TVG 9, Andaman Sea, Andaman Back-Arc basin, crater seamount (CSM), flank, 07°55.924'N, 94°03.139'E to 07°56.036'N, 94°03.026'E, 517-671 m, 25/11/2007.

Description. 7 mm dd, disk pentagonal, arched, dorsally convex, ventrally concave, translucent, arms broken off close to disk, lost. Particles of sediment and/or debris embedded in dorsal integument. Dorsal disk with five-pointed star-shaped central plate with concave edges, bordered by five quadrangular radial infrabasals and five larger, elongated pentagonal interradial basals. Five large pentagonal radial primary plates, with acute distal point and straight proximal and lateral edges separating the radial shields proximally. Interradially a rectangular plate (irl), twice as long as wide, in series with a large pentagonal plate (ir2) with acute distal point, separating the lateral plates of the first segment. Radial shields pentagonal with proximal angle. First dorsal arm plate (d2, associated with second pair of lateral plates) triangular, with proximal angle, separating distal ends of radial shields. Following four dorsal arm plates (d3-d6) rectangular, wider than long, contiguous, decreasing in size along the arm. Last dorsal arm plate (d7) triangular, with proximal angle, straight distal edge, widely separated from previous plate (d6). Lateral arm plates (11-7) elongated, flat, thin, standing erect off the arm at an angle, fused to form an extension of the disk. First lateral plates of one arm fused to

■ Response o f Bent file community structure to the HaBitat Heterogeneity in Indian Ocean 180 | r » i; .• Discovery of species Chapter - 6 the next by their distal ends. In each interradius a fringe of 35 rectangular spines, two to three at each lateral plate, aligned with grooves on the lateral plates. Two short conical spines at arm base at disk edge.

Ventral disk in proximal part with scattered, small translucent scales, distal part formed by the lateral arm plates. Seven arm segments included in disk. Oral shields absent, few scales instead. Madreporite small, oval, with distal, eccentric hydropore. Jaws strongly curved, proximally concave distally convex, diverging. Small pointed apical papilla or tooth, flanked by two similar, small, pointed papillae laterally at dental plate, a small pointed papillae at intersection of dental and oral plate, a wide lateral papilla with jagged edge at oral plate. Adoral shields narrow, bar-like, proximally widely separated, abutting first arm segment. Tentacle pores extremely large, round, lacking scales, second one some distance from mouth slit; decreasing in size distalwards from fourth segment, from seventh pore hardly visible. Ventral arm plates within disk saddle-shaped, rectangular, with strongly concave lateral edges, almost straight distal and proximal edges, contiguous. First ventral arm plate longer than others, distal edge widened with three excavations, proximally with rounded lobe. Large round gonads visible in proximal part of disk. No bursal slits.

Remarks. According to the latest revision, the genus Astrophiura contains eight species (Fujita and Hendler, 2001), which are distinguished by few diagnostic characters due to a lack of sufficient sample sizes for the assessment of intraspecific variability and loss of type material. The specimen presented here differs from A. permira, A. chariplax Baranova, 1955 and A. wanikawa Fujita and Hendler, 2001 in the lack of tubercles and sculpturing of the dorsal disk plates, and from A. chariplax, A. kohurangi McKnight, 1975 and A. wanikawa in the reduced and widely separated adoral shields. Astrophiura marionae Ziesenhenne, 1951 has four plates in the interradial series and a single oval tentacle scale. The type of A. kawamurai Matsumoto, 1912 has been lost (Fujita and Hendler 2001), but according to the original

■Response ofHentHic community structure to tbe Habitat Heterogeneity in Indian Ocean 1811 !• * * Discovery o f species Chapter - 6 description it differs from our specimen in the presence of a tentacle scale, a greater number o f oral papillae and almost fully separated radial shields. Apart from their larger size with 12 mm and 12.5 mm dd, respectively, A. levii Vadon, 1991 and A, tiki differ from our specimen only in the presence of a minute tentacle scale, which may not have developed yet in our smaller specimen. These two species may also be conspecific. Vadon (1991) omitted A. tiki in her work and possibly did not know about its existence. Given these subtle differences it is possible that the actual number of species in the genus is less than eight and describing another one based mainly on the absence of tentacle scales in a single specimen seems not advisable.

Distribution. The genus Astrophiura has a wide Indian Ocean-Indo-Pacific distribution, extending into polar regions. Astrophiura permira was described from Madagascar, but has been found numerous times in South Africa (Litvinova and Smirnov 1981), where the conspecific A. cavallae Koehler, 1915 had been described, and in the Kerguelen (GBIF, record from Russian Academy of Sciences). It is the only species of the genus reported from the Atlantic, off Mexico (GBIF, records from MNHN and UNAM), an extraordinary distance from its type locality and given the great similarity between the species of Astrophiura, these records should be verified. Astrophiura kohurangi was described from the Northern Tasman Sea and has also been found in the Solomon Islands (GBIF, records from MNHN), A. marionae was described from California and has since been found there again (GBIF, records from MNHN and UNAM), A. levii is so far known only from New Caledonia, A. chariplax from the Bering Sea and Sakhalin, A. kawamurai and A. wanikawa from Japan and A. tiki from off Chile. Most of the species have been found at medium depths above 1000 m, only A. chariplax is a bathyal species from 2440 m.

Response of benthic community structure to the habitat heterogeneity in Indian Ocean 182 | r a i> e Discovery o f species Chapter - 6

Genus O phiura Lamarck, 1801

O phiura sp. (Figure 6.C.5)

Material. 1 specimen, 4.5 mm dd, TVG-11, Andaman Sea, Back-Arc basin, Seamount 2 (SM2), flank, 09°59.500'N, 93°57.137’E to 09°59.526’N, 93°57.260'E, 1290-1424 m, 27/11/2007.

Remarks. This specimen has the appearance of a juvenile Ophiura, with three pointed proximal oral papillae and a wide distal papilla (buccal scale). The genital papillae are low, block-like, in a continuous row along the bursal slit, continuing onto the dorsal arm, forming a low comb. There are two short pointed arm spines. Juvenile brittle stars are notoriously difficult to identify (Stohr, 2005) and since the genus Ophiura is one of the largest (Stohr et al., In press) of the genus, we prefer not to attach a name to this single specimen.

Family Ophiactidae Matsumoto, 1915 Genus Ophiactis Ltitken, 1856 Ophiactisperplexa Koehler, 1922 (Figure 6.C.6)

Material. 1 specimen, 4.5 mm dd, TVG 11, Andaman Sea, Back-Arc basin, Seamount 2 (SM2), flank, 09°59.500'N, 93°57.137'E to 09°59.526'N, 93°57.260'E, 1290-1424 m, 27/11/2007.

Diagnosis. Five-armed Ophiactis. Dorsal disk covered by medium sized, round, overlapping scales, among which only the centrodorsal is larger and conspicuous, no spines. Radial shields 1/4 as long as dd, completely separated by scales. Dorsal arm plates triangular, twice as wide as long, contiguous. Three conical, blunt arm spines, slightly longer than a segment. Single distal oral papilla, large, triangular. Apical papilla and teeth tricuspid with pronounced median point. Oral shields (except madreporite) small, triangular

■ Response of benthic community structure to the habitat heterogeneity in Indian Ocean 183 | !> a ;> e Discovery of species Chapter - 6 with distal lobe, as wide as long. Adoral shields narrow, crescent-shaped. Ventral arm plates quadrangular to trapezoid, at distal edge slightly wider than long, contiguous. Single large, oval tentacle scale.

Remarks. Although this specimen measures about half the size of the type specimens (Koehler, 1922), it presents all the characteristics of its species. The large pointed oral papilla is a distinctive character and the separated radial shields, contiguous wide dorsal and contiguous ventral arm plates distinguish the species from others. This is an Indo-Pacific species according to the 160 records found in GBIF, most of them from the area around New Caledonia, Vanuatu and Fiji (MNHN, accessed through GBIF data portal, http://data.gbif.org/datasets/resource/12030, 2011-07-04). It is a new record for the Andaman Sea.

Family Ophiacanthidae Ljungman, 1867 Genus Ophiolimna Verrill, 1899 Ophiolimna antarctica (Lyman, 1879)

Material. 3 specimens, 1.3 mm dd and 1.7 mm dd, TVG 9, Andaman Sea, Andaman Back-Arc basin, crater seamount (CSM), flank, 07°55.924'N, 94°03.139'E to 07°56.036'N, 94°03.026'E, 517-671 m, 25/11/200. 1 specimen, 4.4 mm dd, TVG 11, Andaman Sea, Back-Arc basin, Seamount 2 (SM2), flank, 09°59.500’N, 93°57.137’E to 09°59.526'N, 93°57.260’E, 1290-1424 m,

27/11/2007.

Diagnosis. Both sides of disk densely covered with round granules. In large specimen oral frame naked, in smaller specimens completely covered with granules. Lateral arm plates strongly striated; longest arm spines almost two segments long. Dorsal arm plates triangular, ventral plates pentagonal. Single apical papilla at each jaw tip, three conical lateral oral papillae and a larger, operculiform distal papilla. Oral shield twice as wide as long.

■ Response of benthic community structure to the habitat heterogeneity in Indian Ocean 184 | r> » s f 'Discovery of species Chapter - 6

Remarks.Ophiolimna antarctica is a deep-sea species with wide distribution in the Indo-West Pacific, Arctic and Antarctic (O’Hara and Stohr, 2006). Its occurrence on the Andaman seamounts is therefore not unexpected, but previously not documented.

D iscussion

The discovery of two unknown species in a small collection of six species from seamounts could be taken as evidence of endemism as has long been speculated (McClain, 2007). Considering that the Andaman Sea and the Indian Ocean are undersampled with regard to deep-sea ophiuroids, and taking into account the contrary results by O'Hara (2007), we suspect instead that these species occur on the deep-sea floor, but had not been collected before. The elevated position of the seamount provided access to this elusive fauna. Ophiophyllum, Astrophiura and bathyal species of Ophioleuce are rarely collected and largely unknown, which makes these additional finds particularly valuable. It is suspecting that more unknown species will be discovered with further collecting. The known geographic range of all species found by this study was extended.

The systematics of Ophiuroidea is problematic, in need of revision, due to many inconsistencies between higher taxa and species with difficult to understand combinations of characters (Martynov, 2010). Ophioleuce longispinum sp. nov. is another such species with characters otherwise found in different genera. Further study should reveal whether this is an interesting case of convergent evolution or evidence of phylogenetic relationships.

Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 185 J 1> a « e Discovery of species Chapter - 6

Figure 6.C.I. Ophioleuce longispinum sp. nov., holotype, SEM images. A, dorsal aspect; B, long spines on arm base; C, disk granules; D, disk edge with dislocated spines; E, dorsal arm; F, articulation of long arm spine; G, ventral arm; H, ventral aspect; I, ventral disk; J, proximal aspect of jaws; K, bursal slit. AP, apical papilla; AS, adoral shield; B, bursal slit; DAP, dorsal arm plate; DP, dental plate; GP, genital plate; LAP, lateral arm plate; LSp, long spine; M, madreporite; OP, oral papilla; OS, oral shield; RS, radial shield; T, tooth; TPo, tentacle pore; YAP, ventral arm plate; VSp, ventral spine.

■ Response o f benthic community structure to the habitat heterogeneity in Indian Ocean 186 | P a » c Discovery of species Chapter - 6

Figure 6.C.2. Ophioleuce longispinum sp. nov., arm skeleton, SEM images, A, holotype, B-K, holotype or paratype. A, proximal arm laterally, note the large ventral spine articulations; B, articulations of lateral spines, lower for ventral spine, above for upper, distal edge to left; C, small upper spine, articulation aspect; D, flat ventral spine, articulation aspect; E, dorsal arm plate, external, distal edge left; F, ventral arm plate, middle of arm, external; G, vertebra, proximal arm, dorsal aspect, distal end at left; H, vertebra, proximal aspect; I, lateral plate, ventrolateral aspect, distal to the right; J, lateral plate, ventral aspect, distal to the right; K, lateral plate, internal, distal to the left.

•Response o f bent Hie community structure to the Habitat Heterogeneity in Indian Ocean 187 | f> a g c Discovery of species Chapter - 6

Figure 6.C.3. Ophiophyllum minimum sp. nov., holotype, SEM images. A, dorsal aspect; B, disk edge dorsolaterally, with spines; C, interradial disk with fringe; E, dorsolateral arm base; G, lateral arm; H, ventral arm; I, ventral aspect; J, ventral disk interradius with fringe; K, proximal jaw aspect; L, oral frame. Abbreviations as in Figure 2, and DSp, dorsal spine; IR, interradial plate; OP1, oral plate (half-jaw); VIR, ventral interradial plate.

Response of Benthic community structure to tfie haBitat heterogeneity in Indian Ocean 1881 P a g e Discovery of species Chapter - 6

Figure 6.C.4. Ophiophyllum minimum sp. nov. arm skeleton, SEM images. A, ventral plate, external; B, dorsal plate, external; C, lateral plate, laterally, distal to right; D, lateral plate, spine articulations; E, large ventral spine; F, lateral plate, internal; G, lateral plate, ventral aspect; H, vertebra, dorsal aspect, distal at right; I, vertebra, lateral. SA, spine articulation.

■Response of Bent Hie community structure to the habitat heterogeneity in Indian Ocean 189| P » g e Discovery of species Chapter - 6

■Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 190 | P a g e Discovery of species Chapter - 6

Figure 6.C.6. Ophiactis perplexa: (A) dorsal aspect; (B) ventral aspect; (C) arm dorsally. Ophiolimna antarctica: (D) dorsal aspect; (E) ventral aspect. Scale bars in millimetres.

■ Response o f Benthic community structure to the habitat heterogeneity in Indian Ocean 1911 !> a * e Chapter 7 Summary and Conclusion Summary andconcCusion Chapter - 7

Summary and Conclusion

This study reveals several novel characteristics of macrofaunal communities and their response to habitat heterogeneity on the western Indian continental margin. The physiographic provinces and their related environmental characteristics in the study area generated habitat heterogeneity, which is summarized below together with the corresponding community characteristics.

Shelf: The shelf of western Indian margin was dominated by sandy sediment with low DO. It included part of the OMZ at 50 m, and had moderately high sediment Corg content. The shelf contained the highest abundance and biomass size spectra peak in the 500-1000 g weight class, with moderately high diversity, species richness. Polychaeta was dominant group among the macrofaunal community and CMJ feeding types polychates were dominated the shelf waters.

Slope: The slope was characterized by silty sediment and included the core OMZ and area covered the lower slope with higher Corg. Moderate density was observed with highest biomass peak in the 1000 — 2000 g weight class. Diversity and species richness were lowest and the percentage of SDT feeding types was highest at the upper and lower slope, while CMJ feeding type recorded at mid slope area.

Basin: The basin appears to be a normoxic region with silty texture and lower Corg content. This region displayed the highest diversity, species richness and SDT feeding types fauna dominated in this region. Smaller body size organism found with a biomass peak in the 300 — 500 g weight class in the basin.

Dominant taxa and faunal composition differed along the gradient of habitat heterogeneity. In general, results from the Pakistan margin were weak

■ Response of Benthic community structure to the hahitat heterogeneity in Indian Ocean 192 11- „ * . Summary and conclusion Chapter - 7 predictors for macrofaunal community structure along the Indian margin. The reason for low abundance and biomass in the core and lower boundary parts of the OMZ in the western Indian margin compared to other areas is not clear. Furthermore, the results of the present study did not support our second hypothesis, as macrofaunal abundance and biomass were lower in the OMZ region, except for the shallowest part (48, 50, 102 m) where abundance and biomass were high. Further investigation based on seasonal sampling in the shelf region and high-resolution sampling in the OMZ region is required to understand the community interaction with seasonal environmental changes on the western Indian continental margin.

In the Indian Ocean Basin, manganese nodule are reported in a large area that extends from 10°S to 25°S and 70°E to 86°E by India. As a potential contractor, India under the INDEX programme has conducted different deep- sea experiments in order to collect deep-sea environment data. This study carried out in the abyss of the Central Indian Ocean Basin and aimed to increase the base line information on macrofaunal community structure and their spatial variations as well the interaction with environmental characteristics for future EIA study. The current study reported the highest densities ever, which differed due to the sampling technique and the higher food availability. Amphipoda, Polychaeta and Tanadicea dominated the study area. Homogenously clay silt sediment was found throughout the study area. Due to higher content of sediment Corg, deposit feeding habits macrofauna dominated the area.

This study reveals several novel characteristics of the structure of megafaunal communities and their response to differences within and between the seamount habitats in the Andaman Back-arc Basin, Indian Ocean. The geomorphological settings, bathymetric gradient and substratum types in the study sites generate the habitat differences between the seamounts as follows:

'Response of Bentfiic community st ructure to the BaBitat Beterogeneity in Indian Ocean 193 11! a g <» Summary ancCconcCusion Chapter - 7

CSM. This shallowseamount demonstrated a large component of hard substrates (e.g. boulders and cobbles), with higher species abundance and diversity. The sponge Euplectella sp. was dominant on the flank which was more diverse than the crater summit.

SM2: This seamount is characterized by cobbles and fine sediments types of substratum, with medium faunal abundance and diversity. The bird-nest sponge Pheronema sp. was dominant on the flank. Basin: The basin area was dominated by fine sediments and very poor faunal abundance and diversity. Echinoderms were dominant in the basin area

Faunal composition and diversity differed within and between the seamounts which can be explained by geomorphological features and substratum types. Due to lack of extensive sampling and other environmental data, this study was unable to explain the high species diversity on the shallower seamount. Further study is required to understand the processes involved in creating a high biodiversity, and other aspects, such as biogeography and endemism of megafaunal communities at different seamounts and also at other habitats like the ridge area in the Indian Ocean.

The study from Carlsberg Ridge presents results of an integrated analysis of bathymetric data, associated geoscientific information (e.g., depths and bottom substrates) and benthic megafaunal data investigated through

underwater video. Benthic megafaunal density decreased with increasing depths. Megafaunal community structure was determined by suitable habitat types during the underwater observations. Transects located at shallower depths on off-axial highs area revealed mostly sediments with basalt substratum where Cnidarians were dominant. Deeper transects had a higher variety of substratum types which lead to greater megafaunal diversity with higher abundance of echinoderms and poriferans in this region. Sessile suspension feeding communities, such as poriferans and cnidarians were mostly observed on hard

■Response of Benthic community structure to the habitat heterogeneity in Indian Ocean 1941 r » * ______Summary andconcCusion ______Chapter - 7 bottom habitat types, while mobile groups like echinoderms were dominant on the sediment habitat types. Although taxonomic identification from underwater images or video observations was not always at high-resolution, quantitative information provides a useful baseline for the Carlsberg Ridge as well as a general perspective for the deep Indian Ocean.

Discoveries of new species were the one of the great achievement of this study. A genus and species of Hexactinellid sponges and brittle stars were reported as new to the science and the genus or species name was named as per the nomenclature rules from several unexplored habitats in Indian Ocean.

The new genus and species of Hexactinellid sponge I n d i e l l a gen.nov.

ridgenensis sp.nov. reported frcpn Carlsberg Ridge, and Hexactinellid

Hyalascus andam anensis sp.nov and brittle stars O phioleuce longispinum

sp.nov., and Ophiophyllum minimum sp.nov. were reported from CSM seamount, Andaman Back-arc Basin.

Finally it can be concluded that the present study found the local as well as regional scale biodiversity and their interaction with associated environments from various habitat located in the Indian Ocean. This study will be useful as a baseline for the western Indian continental margin, deep-sea abyss in CIOB, seamount region and mid-oceanic ridge in Indian Ocean which is poorly

investigated.

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'Response of Benthic community structure to the habitat heterogeneity in Indian Ocean224 | A ppendix 1

Taxonomic list of megafaunal communities from Amdaman Back-arc Basin including seamounts

Taxa CSM- CSM- SM2- SMI- Off-axial Rift Summit Flank Surnmit Flank highs valley Euplectella sp - + " - - -

Pheronema sp - + + + - -

Ferrea sp " + - - " -

Hyalascus andamanensis + - -

Hyalonema sp - - " " - +

Aphrocallistes bocagei - + " -

Demospongiael " + + - +

Radiella sol - + - -

Hexactinellidal - - + - * -

Demospongiae 2 + - - -

Demospongiae 3 - - - + - -

Ophiophyllum sp l - + “ - - -

Ophiophyllum sp2 - + - - *

Ophiolimna a n ta rc tic a - + - " -

Uphiolepis sp - + - -

Ophiura sp + + - + "

Dphiuroidea sp .l + + - - +

Asteroidea sp .l + + - +

Holothuroidea sp. 1 - + - - - "

holothuroidea sp .2 + + - -

Eolothuroidea sp.3 - + - +

Echinoidea - + - -

Erinoidea sp .l - + - + - -

vm n ella sp - - + + +

^ a lliu m sp - + - - - " L eiopathes sp + - - - -

Octocorallia sp.l " + - - - -

Octocorallia sp .2 - + - - - -

Octocorallia sp .3 " + - - " -

Gorgonacea sp.l - - + - -

Gorgonacea sp .2 " + + - -

Gorgonacea sp .3 - + - - - -

Paragorgiidae sp.l - + + - - -

Antipathidae sp.l - + - + - -

Actiniaria sp .l “ + - - - -

Actiniaria sp .2 + + - - " +

Actinoscyphia sp - + - - - -

Pennatulacea sp. 1 - + - -

Pennatulacea sp.2 - + - - - -

Nudibranch - + - - - -

Chirostylidae sp.l - + - - - -

Galatheidae sp. 1 + + - - - -

Lithodidae sp. 1 - + - - - -

Decapoda sp. 1 (Crab) + - " - - -

Decapoda sp.2 (Spider + “ - - * crab) Decapoda sp .3 (S h rim p ) - + - - - -

Decapoda sp .4 (S h rim p ) - + - - - "

Decapoda sp .5 (S h rim p ) - " - + - -

A m m oth ella sp - + - -

Liogalathea laevirostris - + - -

M unida sp - + - -

Valvifera “ " +

Neotanaidae " + -

Anguilliformes + + - - -

Uasmobranchii 1 - - + + + Actinopterygii sp.l + + - - - -

Actinopterygii sp .2 - + - "

Sipuncula “ + - + - - A p p e n d i x 2

Megafaunal taxon list (presence and absence data) observed during underwater video survey in Carlsberg Ridge

T axa T V G 2 T V G 3 O F O S 1 O F O S 2 O F O S 3 T V G 1 T V G 4 T V G 5 T V G 6 T V G 7 T V G 8

Xenophyophore sp. 1 - - + - - - -

Hexactinellida sp.l ------

Hexactinellida sp .2 ------

Hexactinellida sp .3 - - + ------

Hexactinellida sp .4 - - + ------

Hexactinellida sp .5 - - + - - - - - +

Hexactinellida sp.6 - - + - - - - -

Hexactinellida sp .7 - - + ------

Hexactinellida sp.8 ------

H yalonem a sp - - + - + - - - * -

Hexactinellida sp .9 - - + ------

Hexactinellida sp .10 - - + ------

Hexactinellida sp.l 1 - - + + ------

Hexactinellida sp .l2 - - + ------

Hexactinellida sp.l3 - - + ------

Hexactinellida sp .14 - - + ------

C hon elasm a sp - - + ------

Hexactinellida sp. 15 ------

Hexactinellida sp. 16 - 4- - + - - - - +

Hexactinellida sp. 17 - + ------HexactineJJida sp. 18 1 + -f------Hexactinellida sp. 19 + + ------Hexactinellida sp .20 ------* - Hexactinellida sp .2 1 + + - - -

Hexactinellida sp .22 - - + - - - - -

Hexactinellida sp .23 - - + ------

Hexactinellida sp .24 ------

Hexactinellida sp .25 - - + ------

Hexactinellida sp .26 ------

Chrysogorgia sp. 1 ------

Octocoral sp. 1 - - + ------

Octocoral sp.2 - - + ------

Gorgonian sp.l + + ------

Gorgonian sp.2 + + ------

Gorgonian sp .3 + + ------

Gorgonian sp.4 ------

Gorgonian sp.5 ------

Gorgonian sp.6 ------+ - - -

Whip coral sp. 1 - - + + - + - - - -

Whip coral sp .2 + + + - + - + - + +

Actinaria sp.l - - + ------

Actinaria sp.2 - - + ------

Actinaria sp.3 +• + ------+ - -

Actinaria sp.4 - - + ------

Stalk Crinoidea - + - * ------_ , ; ' A ster o id sp. I - _ - - ' - - - + Asteroid sp .2 - - + - - - - - • Asteroid sp.3 - - - - + - - ■ + •

Asteroid sp .4 + - - - - - ■ - ■

Brisingid sp. 1 - + - - - + ■ + -

Brisingid sp.2 + + - - - - ' • • ■

Ophiuroidea sp. 1 - - + - - - ' - ■

Ophiuroidea sp.2 - - - - + - ' - - -

Ophiuroidea sp .3 + - + ------

Ophiuroidea sp.4 - - + - - - - - +

Ophiuroidea sp.5 ------

Ophiuroidea sp.6 - - - - ' - - + H- +

Ophiuroidea sp.7 - - - - + - * - - +

Crinoidea sp. 1 - + - - - - - * - - ■

Echinoidea sp. I ------

Echinoidea sp.2 - - 4* - - + - - + + •

Polychaeta sp. 1 - - - - -1------

Holothuroidea Sp. 1 - - + ------■

Holothuroidea Sp.2 - - - - + - - + + - -

Holothuroidea sp .3 - - - + + ------

Holothuroidea sp .4 - - - + ------

Holothuroidea sp.5 + - + - 4- + - + + +

Holothuroidea sp.6 ------+ -

Holothuroidea p .7 - - - + - - - - -

Enypniastes sp - + + - - - ' - - H olothuroidea sp .8 _ - + + - - + ■+■ | + 4- Galtheidae sp.l - + - - - - - Galatheidae sp.2 - - - - + ------

Anguiliformes sp. 1 - - + - - - - -

Synaphobranchid + " - • - “ sp .l Unidentified - - - + " " - chordate sp. 1 Anguiliformes sp.2 - - - - - + - + +

Unidentified + + + " + chordate sp.2 Unidentified - - + - “ - ~ chordate sp.3 Anguiliformes sp.3 + ------~

Anguiliformes sp.4 + ------

Anguiliformes sp .5 + + ------

H alosau r sp. 1 - + ------+ -

Unidentified - - - - - + - chordate sp.4 Unidentified ------+ + + chordate sp.5

Unidentified - + ------chordate sp.6

Unidentified “ - - + - - - * - - chordate sp .7 Plesiopenaeus sp. 1 - + + + + - + + + +

Unidentified - " - - - + - Decapoda sp. 1 unidentified " + - - - - + + “ Brachyuran sp. 1 Publications List of publications

1. Sautya S., Ingole B., Ray D., Stohr S., Samudrala K., Kamesh Raju K.A., Mudholkar A. 2011. Megabenthic community structure within and between deep- sea habitats: An investigation from seamounts and ridge area in the Indian Ocean. PLoS ONE, 6(1), el6162. Doi:10371/joumal.pone.0016162.

2. Sautya S., Tabachnick K.R., Ingole B. 2011. A new genus and species of deep- sea glass sponge (Porifera: Hexactinellida: Aulocalycidae) from the Indian Ocean. Zookeys, 136, 13-21

3. Sautya S., Tabachnick K.R., Ingole B. 2010. First record of the genus Hyalascus (Hexactinellida: Rossellidae) from the Indian Ocean with description of a new species from a volcanic seamount in the Andaman Sea. Zootaxa, 2667, 64-68.

4. Stohr S., Sautya S., Ingole B. 2012. Brittle stars (Echinodermata: Ophiuroidea) from seamounts in the Andaman Sea (Indian Ocean) - a first account, with descriptions of new species. Journal of Marine Biological Association, UK, 92 (5), 1195-1208 doi: 10.1017/S0025315412000240.

5. Ingole B.S., Sautya S., Sivadas S., Singh R., Nanajkar M. 2010. Macrofaunal community structure in the Western Indian Continental Margin including OMZ. Marine Ecology, 31, 148-166.

6. Ingole B., Singh R., Sautya S., Dovgal I., Chatterjee T. 2009. Report of epibiont Thecacineta calix (Ciliophora: Suctorea) on deep-sea Desmodora (Nematoda) from the Andaman Sea, Indian Ocean. Journal o f Marine Biological Association, UK2-Biodiversity Records. 4 pp. OPEN 3 ACCESS Freely available online • PLos one Megafaunal Community Structure of Andaman Seamounts Including the Back-Arc Basin - A Quantitative Exploration from the Indian Ocean

Sabyasachi Sautya1*, Baban Ingole1, Durbar Ray1, Sabine Stohr2, Kiranmai Samudrala1, K. A. Kamesh Raju\ Abhay Mudholkar1 1 National Institute of Oceanography (CSIR), Dona Paula, Goa, India, 2 Department of Invertebrate Zoology, Swedish Museum of Natural History, Stockholm, Sweden

Abstract Species rich benthic communities have been reported from some seamounts, predominantly from the Atlantic and Pacific Oceans, but the fauna and habitats on Indian Ocean seamounts are still poorly known. This study focuses on two seamounts, a submarine volcano (cratered seamount - CSM) and a non-volcano (SM2) in the Andaman Back-arc Basin (ABB), and the basin itself. The main purpose was to explore and generate regional biodiversity data from summit and flank (upper slope) of the Andaman seamounts for comparison with other seamounts worldwide. We also investigated how substratum types affect the megafaunal community structure along the ABB. Underwater video recordings from Television guided Gripper (TVG) lowerings were used to describe the benthic community structure along the ABB and both seamounts. We found 13 varieties of substratum in the study area. The CSM has hard substratum, such as boulders and cobbles, whereas the SM2 was dominated by cobbles and fine sediment. The highest abundance of megabenthic communities was recorded on the flank of the CSM. Species richness and diversity were higher at the flank of the CSM than other are of ABB. Non-metric multi-dimensional scaling (nMDS) analysis of substratum types showed 50% similarity between the flanks of both seamounts, because both sites have a component of cobbles mixed with fine sediments in their substratum. Further, nMDS of faunal abundance revealed two groups, each restricted to one of the seamounts, suggesting faunal distinctness between them. The sessile fauna corals and poriferans showed a significant positive relation with cobbles and fine sediments substratum, while the mobile categories echinoderms and arthropods showed a significant positive relation with fine sediments only.

Citation: Sautya S, Ingole B, Ray D, Stohr S, Samudrala K, et al. (2011) Megafaunal Comm unity Structure of Andaman Seamounts Including the Back-Arc Basin - A Quantitative Exploration from the Indian Ocean. PLoS ONE 6(1): e16162. doi:10.1371/journal.pone.0016162

Editor: Martin Solan, University of Aberdeen, United Kingdom Received September 8, 2010; Accepted December 8, 2010; Published January 31, 2011 Copyright: © 2011 Sautya et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: The CenSeam (Global Census of Marine Life on Seamount) provided the financial support to identify the benthic invertebrates and publish the data. The funders had no role in study design, data collection and analysis, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

* E-mail: [email protected]

Introduction history, the same is true for the continental slope. The marine fauna in general is extremely undersampled, with an estimated 70- T h e exploration of the fauna associated with seamounts, 80% of marine species remaining to be discovered [7], Thus, underwater mountains of mostly volcanic origin, began over 50 claims of endemism should be made with great caution, but the years ago, after their initial discovery in the 1940s fl]. Originally, species rich environments on seamounts offer an opportunity to only structures of at least 1,000 m in height were included in the sample and study rare species with wide distributions. Since term seamount, but today the smallest topographic features seamount summits are found at shallower depths than the termed seamount are merely 50 100 m in height [2]. Some surrounding bathyal sea floor, they are more accessible for studies have suggested that seamounts evolutionarily and ecolog research. ically ‘function as island groups’ [3], and potentially show a high Seamounts function as hotspots for pelagic organisms, mainly degree of endemism. However, although different seamounts have fish, which has lead to overexploitation [8], The benthic been shown to harbor different and species rich faunas, observed communities, which attract these fish, and the interactions endemism may be an artifact of undersampling [4], [5]. Few large between pelagic and benthic organisms, are little understood. An studies that compare data from a wide range of habitats on increase in knowledge on seamount ecology is thus vital for the seamounts and non-seamount areas have been conducted so far. management of a sustainable fishery and the protection of these For brittle stars, an abundant benthic group, O ’Hara [6] found no vulnerable habitats. difference in species richness and rates of endemism between Due to volcanic and hydrothermal processes, seamounts build ^amounts ™d non-seamount areas in the Pacific Ocean. He up metal deposits that are potentially interesting for high- °und that, while seamounts vary in their faunal composition, in technology industries [9]. Large scale mining on seamounts may 'Penes richness and endemism, probably due to differences in have severe consequences for the ecology of a whole region. etr environment, as well as their geological and biological Documentation of the faunal communities living on these

pt-oS ONE www.plosone.org 1 January 2011 | Volume 6 | Issue 1 | e!6162 A peer-reviewed open-access journal ZooKeys 13 6 : 13 - 2 1 (2 0 1 1 )

d0j: 10.3 8 9 7 /zookeys. 13 6 . 16 2 6 RESEARCH ARTICLE ^ZooKeys

jvww.zookeys.org Launched to accelerate biodiversity research

A new genus and species of deep-sea glass sponge (Porifera, Hexactinellida,Aulocalycidae) from the Indian Ocean

Sabyasachi Sautya1!, Konstantin R. Tabachnick2’*, Baban Ingole1^

. I National Institute o f Oceanography, Dona Paula, Goa, 403004, India 2 Institute o f Oceanology Ac. o f Sc. o f Russia, N a h im o vsky 3 6 , M o sco w , 1 1 7 9 9 7 , R ussia

f urn:lsid:zoobank.org:author:580EDE04-9E83-46El-AD61-4768B3531504 J um:lsid:zoobank.org:author:AC4DFA99-C6lA-45C5-A4lF-746736EF63EF § urndsid:zoobank.org:author:575B6C4E-B6B7-49F6-A53E-23688D087C2C

Corresponding author: Sabyasachi Sautya ([email protected] )

Academic editor: R. Pronzato | Received 30 M ay 2 0 1 1 | Accepted 12 September 2 0 1 1 | Published 13 O cto b er 20 1 1

urn:lsid:zoobank.org:pub:E55BEC!Dl-D81E-4713-A7E5-5FA7F5DEA6C7

Citation: Sautya S, Tabachnick KR, Ingole B (2 0 1 1 ) A new genus and species of deep-sea glass sponge (Porifera,

Hexactinellida, Aulocalycidae) from the Indian Ocean. ZooKeys 136: 13- 2 1 . doi: 1 0 .3 8 9 7 /zookeys. 1 3 6 .1 6 2 6

Abstract New hexactinellid sponges were collected from 2589 m depth on the Carlsberg Ridge in the Indian Ocean during deep-sea dredging. All fragments belong to a new genus and species, In d ie lla gen. n. ridgenensis sp. n., a representative o f the family Aulocalycidae described here. The peculiar features of this sponge, not described earlier for other Aulocalycidae, are: longitudinal strands present in several layers and epirhyses channelization.

Keywords Porifera, Hexactinellida, Aulocalycidae, glass sponge, new genus, new species, Carlsberg Ridge, Indian Ocean

Introduction

Tie family Aulocalycidae was established by Ijima (1927) for 5 genera (Fig. 1): Auloca- kx Schulze, 1886, Rhabdodicyum Schmidt, 1880, Tretopleura Ijima, 1927, Euryplegma Schulze, 1886 and Fieldingia Kent, 1870. One genus Ijimadyctyum Mehl, 1992 was

Copyright Sabyasachi Sautya et ai This is an open access article distributed under the terms of the Creative Commons Attribution License, which Derrnits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This phi H i.-rsy.dc-t: by Pisyiiss:;; ‘sess for privaia/rs'.saicif use, CotTiiUercuh su;s e; uua'i/ssjua ■ puhli:.: library or website is prohibited,

First record of H yalascu s (Hexactinellida: Rossellidae) from the Indian Ocean, with description of a new species from a volcanic seamount in the Andaman Sea

SABYASACHI SAUTYA1, KONSTANTIN R. TABACHNICK2 & BABAN INGOLE' 'National Institute of Oceanography (CSIR), Dona Paula, Goa, 403004. INDIA. E-mail: [email protected] ; [email protected] Institute o f Ocean ology Ac. o f Sc. o f Russia, N ah im ovsky 36, M oscow, 117997, Russia. E-mail: [email protected]

Abstract

A new species o f H y a la sc u s is described from the submarine volcanic crater seamount of Andaman Back-arc Basin, Indian Ocean. The genus was previously known in the Pacific Ocean only.

Key words: Hexactinellida; H y a la s c u s ; new species; seamount; Back-arc Basin; Andaman Sea; Indian Ocean

Introduction

H y a la s c u s was established by ljima in 1896 for a sponge from Sagami Bay (Japan). The genus comprised eight doubtless species until now; H. baculifer (Schulze, 1886); H. stellatus (Schulze, 1886); H. sagamiensis ljima, 1896; H. giganteus ljima, 1898; H . s im ilis ljima, 1904; II. attenuatus Okada, 1932; H. anisoactinus Tabachnick & Levi, 2004; and H. pinulohexactinus Tabachnick & Levi, 2004; all occurring in the Pacific Ocean only. Hyalascus hodgsonii Kirkpatrick, 1907 from the Antarctic Ocean appears to be a doubtful representative of the genus due to the presence of two types of microdiscohexasters; one with numerous secondary rays, and another possessing a reduced number of these rays. The transfer of this species to S c y p h id i u m by Tabachnick & Levi (2004) appears reasonable since presence of two types of discoidal microscleres is the diagnostic character for S c y p h id iu m (Tabachnick, 2002). The assignment by Koltun (1964) o f Hyalascus attenuatus Okada, 1932 to the synonymy of Aulosaccus schulzei ljima, 1896 was rejected later (Tabachnick, 2002). Koltun found two specimens, identified by him as Hyalascus attenuatus , with large spherical discohexasters. As a consequence, these specimens should be regarded as representatives of A u lo s a c c u s ljima, 1896. In part, Ijima's decision was derived from the observation that hypodermal pentactins were absent in A u lo s a c c u s (cf. ljima, 1904). Nevertheless, Okada (1932) noticed that this trait does not seem to be important, as opposed to the large discohexasters, judged a more reliable diagnostic character for Aulosaccus. Some hypodermal pentactins may be present in the latter. Following this argument, later inadvertently supported by Tabachnick (2002), A. mitsukurii ljima, 1898 (1904, 1928) from Sagami Bay (Japan), w a s referred to H y a la s c u s . This was a mistaken decision nevertheless, as this species has two distinct types of discoidal microscleres and should finally be considered a doubtless representative of S c y p h id iu m Schulze, 1900. H y a la s c u s is defined as Rossellinae with saccular body and only one type of discoidal microscleres-the smallest ones m icrodiscohexasters. Dermalia are pentactins and stauractins, hypodermal pentactins (if present) have orthotropal ta n g en tia l rays (T abachnick, 2 0 0 2 ).

64 Accepted bv E. Hajdu: 5 Oct. 2010; published: 4 Nov. 2010 lowi'Hij) of the M arine Bjofogicrtl Aisoannon of the United Kingdom, 2012, 92(5), 1195-1208. <' Marine Biological Association of the United Kingdom, 2012 doi.10.io17/S0025315411000240 Brittle stars (Echinodermata: Ophiuroidea) from seamounts in the Andaman Sea (Indian Ocean): first account, with descriptions of new species

SABINE STOHR1, SABYASACHI SAUTYA" AND BABAN INGOLE2 'Swedish Museum of Natural History, Box 50007, 10405 Stockholm, Sweden, 2National Institute of Oceanography (Council of Scientific & Industrial Research—CS1R), Dona Paula, Goa 403 004, India

For the first lime, brittle stars were collected on two seamounts in the Andaman Back-arc Basin. O f the six species, two were new to science ami arc described herein as O phioleuce longispinum sp. nov. and O phiophyllum m inim um sp, nov., in the family Ophiuridae, subfamilies Ophioleucinae and Ophiurinae, respectively. Skeletal details were studied and documented by scanning electron microscopy. Morphological similarities between related species are discussed in detail. Ophioleuce longis pinum sp, nov. is particularly interesting, because it combines characters typical for its genus with those otherwise only known from Ophiophyllum, such as a limpet-likc disc, a fringe of marginal disc papillae or spines, and a paddle-like modified lower arm spine. The remaining species, Astrophiura cf. tiki, Ophiactis perplexa, Ophiolimna antarctica and an unidentified Ophiura, are new records for the Andaman Sea.

Keywords: Ophiophyllum , Ophioleuce, Astrophiura, taxonomy, systematics, morphology, scanning electron microscopy

Submitted 16 September 2011; accepted 2 February 2012; first published online 28 March 2012

INTRODUCTION ophiuroid for the Indian Ocean (Stohr et al., in press), about a quarter of them endemic to the region. By compari The brittle star fauna of the Indian Ocean is less well known son, the same study found 831 species for the Indo-Pacific. than that of the North Atlantic (Mortensen, 1933; Paterson, This numerical difference may however reflect differences in 1985; Stohr & Segonzac, 2005) or eastern Pacific (O’Hara & collecting effort rather than actual differences in species Stohr, 2006) and the knowledge about the ophiuroid fauna richness. in Indian waters is limited. Early accounts of Indian echino- Seamounts are submarine mountains, often of volcanic derms were published by Bell (1887). Cruises on the Indian origin, elevated from the deep-sea floor. Initially, they were vessel ‘Investigator’ contributed some more material in the thought to be centres of endemism and high species richness, late 19th Century (Koehler, 1897, 1898, 1899) as did the due to their isolated position (McClain, 2007). For ophiuroids John Murray Expedition 1933-1934 (H.L. Clark, 1939), but however, O’Hara (2007) found no elevated levels of endemism progress was slow . James (1970a, 1970b, 1981, 1982a, or species richness on seamounts in general, although individ 1982b) reported on shallow water species in Indian coastal ual seamounts may vary greatly from each other in faunal waters, particularly the Andaman and Nicobar Islands, but composition. In general, seamounts reflect the fauna of the records of Indian deep water species are scarce. He also pro surrounding deep-sea floor at the same depth. For the pur vided a review on the status of knowledge about Indian echi- poses of biological inventories, seamounts are valuable, noderms (James, 1983) to which not much has been added because, once known, they are easily located structures that i since. can be observed and sampled. Particularly, rare species of Recent studies on Indian Ocean ophiuroids have focused the deep sea with limited geographical distribution and/or i °n the area around the Mascarene archipelago in the tropical low densities may go unnoticed for a long time, despite centu eastern Indian Ocean (Guille & Ribes, 1981; Guille & Vadon, ries of ocean exploration. Ophiuroids are a dominant com i '985, 1986; V adon, 1991; Rowe & R ich m o n d , 2004; Stohr ponent of the deep-sea benthic fauna (Gage & Tyler, 1991). ef < 2008). An inventor)’ of shallow water echinoderms of Yet, until now, none have been recorded from Indian water i the Indo-West Pacific was compiled by Clark & Rowe seamounts, according to the Seamount Online database *>971) forty-one years ago and it is still the standard reference (http://searnounts.sdsc.edu). ewk on the subject. A recent census counted 319 species of A multidisciplinary research programme has been initiated by Indian researchers to explore the Andaman Back-arc Basin (ABB), including seamounts. The ABB is an active marginal basin and a part of the major island arc-trench system in Responding author: the north-eastern Indian Ocean. It marks the eastern bound

..'’sii: sabine.stohu7 nrm.se ary of the Indian plate where it sub-ducts beneath the

1195 Marine Ecology. ISSN 0173-9565

SPECIAL TOPIC Macrofaunal community structure in the western Indian continental margin including the oxygen minimum zone Baban S. Ingole, Sabyasachi Sautya, Sanitha Sivadas, Ravail Singh & Mandar Nanajkar

National Institute of Oceanography (Council of Scientific & Industrial Research), Dona Paula, Goa, India

Keywords Abstract Arabian Sea; continental margin; deep sea; habitat heterogeneity; macrofauna; oxygen Patterns of macrofaunal distribution were studied along the western Indian minimum zone. continental margin to distinguish the role of habitat heterogeneity in generat ing and maintaining community structure. A transect perpendicular to the Correspondence coast at 14°N latitude was selected for seabed sampling. Eight stations were Baban S. Ingole, National Institute of sampled in the depth range 3 4 -2 5 4 6 m and characterized with respect to mac Oceanography (Council of Scientific & rofaunal composition, abundance, biomass, diversity and feeding type. The sed Industrial Research), Dona Paula, Goa, 403004, India. iments in the shelf region (34, 4 8 , 100 m) and upper slope (525 m ) were E-mail: [email protected] characterized by silty and sandy facies, whereas the mid slope (1001 m), lower slope (1524 m) and basin (2001, 2546 m) consisted of clayey silts. The highest Accepted: 18 November 2009 value of sediment chlorophyll-a (Chl-a) and total organic carbon (Corg) were recorded from the mid slope areas. Faunal abundance and biomass increased doi: 10.1111/j. 1439-0485.2009.003 56.x from the shallow to deeper depths in the shelf region, and decreased in the slope region (525-1001 m) due to the reduced bottom-water oxygen. The com munity parameters showed an overall increase in both the lower slope and basin areas. A total of 81 macro-invertebrate species belonging to five major groups represented the macrofauna of the area. Polychaeta was the major group at all depths. Among polychaete families, species of the Spionidae, par ticularly Prionospio pinnata, predominated at the oxygen minimum zone (OMZ) core and Cossuridae dominated in the lower part of the OMZ in sedi ments of the mid slope region (1001 m depth). Species diversity was higher in the basin than in the slope region. Fluctuations in diversity appear to be partly due to the bottom-water dissolved oxygen (DO) gradient which includes values that are below the oxygen tolerance of many benthic species. Further, Marga- lefs index (d) and Shannon-Wiener index (H') showed a significant negative (P < 0.01 ) relationship between sediment Chl-a and Corg, suggesting food availability as a critical factor in species dominance. Results of multivariate analyses suggest that for continental margin fauna, different physiographic provinces and an oxygen gradient have a higher influence on the species com position and diversity than other oceanographic conditions.

Problem sublittoral to the abyssal zone, has various interesting habitats that can be described by geomorphological fea In the past few decades, considerable attention has been tures (e.g. shelf, slope, rise, marginal highs, etc.) and their given to the study of continental margin biodiversity related environmental conditions (e.g. depth, pressure, (Flach & Thom sen 1998; Tselepides et al. 2000; Palma temperature, salinity, light, dissolved oxygen, sediment etal. 2005). The continental margin, extending from the characters and other biogeochemical features). All of these

148 Marine Ecology 31 (2010) 148-166 © 2010 Blackwell Veriag GmbH I.vrint Biodiversity Records, page 1 of 3. © Marine Biological Association of the United Kingdom, 2010 Jriio.ioi7/S1755J«7M9990777; Vol. 3; 646', 20.10 Published online Report of epibiont Thecacineta calix (Ciliophora: Suctorea) on deep-sea Desmodora (Nematoda) from the Andaman Sea, Indian Ocean

BABAN INGOLE1, RAVAIL SINGH*, SABYASACHI SAUTY a ’, IGOR DOVGAL2 AND TAPAS CHATTERJEE3 'National Institute of Oceanography, Dona Paula (CSIR), Goa-403 004, India, 2Schmalhausen Institute ot Zoology, B. Khmelnitsky Street, 15, 01601, Kiev, Ukraine, ^Indian School of Learning, ISM Annexe, PO-ISM , Dhanbad 826004, Jharkhand, India

Suctorian epibionts Thecacineta calix attached on the cuticle of nematodes Desmodora sphaerica and D. pontica are reported herefrom the deep-sea hexactinellid sponge Pheronema sp. from the Andaman Sea (Indian Ocean). The epibiont T. calix is reported here for first tim e fro m the A ndam an Sea.

Keywords: epibionts, suctorians, Thecacineta calix, deep-sea, nematodes, Desmodora, Andaman Sea, Indian Ocean

Submitted 2 October 2008; accepted 8 January' 2010

INTRODUCTION Island, 9°59'3t.52"N 93°57'i548"E, from a water depth of 1301 m. Upon collection, the sponges were carefully separated Suctorian ciliates are common epibionts on benthic marine from the sediment and immediately preserved with absolute and interstitial invertebrates like harpacticoid copepods, alcohol. In the laboratory, the sponge samples were washed nematodes, halacarid mites etc. (Jankowski, 1981; Dovgal, carefully and the entire faunal community associated with 1996; Dovgal et al, 2008). A number of suctorian ciliate ecto- sponge spicules were sorted out carefully and identified to commensals have been observed occurring on the cuticle of the lowest possible taxa. All the nematodes were separated various members of the family Desmodoridae (Allgen, 1952, and fixed in 5% formalin. Nematodes were identified to 1955; Matthes, 1956). In the present study, suctorian ciliates genus/species level according to Platt & Warwick (1983) and have been recovered on the cuticle of two nematode species using on-line recent literature (www.nemys.ugent.be). Desmodora sphaerica and D. pontica belonging to the Measurements of ciliates were made using the computer Desmodoridae family isolated from the deep-sea sponge program Scope Photo v. 2.0 for processing of digital images. Pheronema sp. from the Andaman Sea. Scrupulous micro For slide preparation the material was stained by Boehmer’s scopic observations revealed suctorian epibionts are conspeci- haematoxylin and mounted in Canada balsam. Permanent fic with Thecacineta calix. Thecacineta calix is reported here slides of infested nematodes were deposited in the collections for first the tim e from the A n d am an Sea. of the Department of Fauna and Systematics of Invertebrate Animals of the Schmalhausen Institute of Zoology, National Academy of Sciences, Ukraine and in the museum of Biological Oceanography, National Institute of Oceanography, MATERIALS AND METHODS Goa, India.

As part of a deep-sea study of benthic biodiversity, sediment sampling was performed in the Andaman Back Arc Basin RESULTS AND DISCUSSION (Figure 1) during the RV ‘Sonne’ cruise (NIO-RVS-II, 17 October to 1 December 2007). Seabed samples were obtained Nematodes species Desmodora sphaerica a n d D. pontica, Fy deploying a TV camera-guided grab (area: 0.6 m 5) which belonging to the genus Desmodora of the family consists essentially of a set ot steel jaws witli a video camera Desmodoridae associated with a deep-sea hexactinellid in the centre. It collected sediment and rock samples and sp onge Pheronema sp., were used for the present study. transmitted pictures of the ocean floor to the deck unit. A total of 71 specimens of nematodes belonging to six Some specimens of hexactinellid sponge were collected species were isolated from the deep-sea Pheronema sp. O f along with the sediment and rock samples taken from the these, five (Desmodora sphaerica, D. pontica, D. schulzi, uPPer slope of the Northern Seamount located off Nicobar Desmodora sp .i a n d Desmodora sp.2) belonged to the family Desmodoridae and one specimen could not be identified as it was damaged. Among these, D. sphaerica (17 individuals ^responding author: l Dovgal out of 71 specimens of nematodes collected) and D. pontica £»* [email protected] (12 individuals out of 71 specimens of nematodes collected)

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