Biodiversity of Free-Living Marine Nematodes from Arabian Sea of Pakistan

Biodiversity of free-living marine nematodes from Arabian Sea of Pakistan

Item Type article

Authors Kazi, Nasira; Kamran, Muhammad; Fayyaz, Shahina; Nasreen, Hajra; Israr, Muhammad

Download date 10/10/2021 07:28:22

Link to Item http://hdl.handle.net/1834/40758 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 01-06, 2011.

BIODIVERSITY OF FREE-LIVING MARINE NEMATODES FROM ARABIAN SEA OF PAKISTAN

Nasira Kazi, Muhammad Kamran, Shahina Fayyaz, Hajra Nasreen, Muhammad Israr National Nematological Research Centre, University of Karachi, Karachi -75270, Pakistan (NK, MK, SF); Jinnah University of Women, 5-C, Nazimabad, Karachi, Pakistan (HN); Pakistan Science Foundation, 1-Constitution Avenue, Sector G-5/2, Islamabad, Pakistan (MI). email: [email protected]

ABSTRACT: Biodiversity patterns of free-living marine nematodes communities were assessed by certain diversity measures in different localities of Sindh and Balochistan viz., Ibrahim Haidry, Korangi Creek, Clifton, Keamari, Sandspit, Hawksbay, Paradise Point, Mubarak Village, Gadani and Sonmiani. A total of eighty nine nematodes were gathered from the studied areas which belong to sixty one nematode genera and twenty six families of five orders. The highest number of nematodes (30) was recorded from Sandspit beach and lowest (15) was from Mubarak village. The studied area exhibited spatial variation in nematode biodiversity patterns. The species diversity indices demonstrate that Sandspit is the most stressed area where as Mubarak Village is the least stressed area among the ten sampling spots.

KEYWORDS: Shannon Weiner, Diversity index, Species richness, Abundance, Evenness, Arabian Sea.

INTRODUCTION

Nematodes are the most abundant and in terms of species diversity the richest group of meiofauna in the benthos of aquatic ecosystems (Traunsperger, 2000, 2002). The meiofauna is defined as all metazoans retained on a sieve of 42 µm (Mare, 1942). Meiofauna occur in both fresh water and marine habitats, although most ecological studies on meiofauna have been performed in the marine environment. Meiofauna occur in the splash zone on the beach up to the deepest sediments in the sea; they are found in all types of sediments. In almost all meiobenthic studies, the majority of the fauna has been found in the upper 2 cm of sediment (Vincx, 1996). Nematodes comprise the largest animal Phylum in terms of density and number of species (Blaxter et al. , 1998). Among them free-living marine nematodes are found in highest abundance in a variety of sediments and surfaces of intertidal and benthic zones. Biodiversity measurements are only relevant if they can be calculated from the samples taken on a quantitative basis. When pollution is present or a human disturbance has occurred in a community, biodiversity is typically lower than in an undisturbed community. Biological diversity defined as “The variability among living organisms from all sources, including inter alia, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems”. This definition represents three aspects of diversity, namely ecosystems, species and 2 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 2011. genus. So the study of biodiversity draws primarily upon the disciplines of taxonomy and classification, biogeography, ecology, genetics, popul-ation biology and evolution biology (Lambshead, 2004).

MATERIALS & METHODS

Water and sediment samples were collected from ten localities of Sindh and Balochistan coasts during 2005-2007 to estimate the nematodes diversity, richness and evenness. A diversity index is a mathematical measure of species diversity in a community. The Shannon diversity index (H’) is commonly used to characterize species diversity in a community. Shannon’s index accounts for both abundance and evenness of the species present. The Shannon Weiner index (H’), richness (d 1) and evenness (J) were calculated with the formulas described below:

Shannon Weiner diversity index: The diversity index (H’) was computed after Shannon and Weaver (1949) information theory function.

H’= -∑ pi log pi

Where pi is the proportion of total number N belonging to the i-th species.

Species richness: The species richness is simply the number of species present in an ecosystem. Species richness was determined using the formula of Menhinick (1964) as follows:

d= S/ √

Where S is equal to the number of species and N is the total number of individuals of all species.

Equitability or Evenness (J): Which describes the evenness of allotment of individuals among the species was calculated as the observed diversity as a proportion of maximal diversity in that area. It was calculated according to Pielou, (1969) as:

Equitability (J’) = H’/H max = H 1/log S

Data Analysis: Nematodes data were used to calculate the diversity as the number of species per sample (S), the Shannon Weiner diversity index (H 1 calculated using naperian logarithms) Shannon and Weaver (1949). Evenness was calculated using Pielon Kazi et al.: Free-living marine nematodes from Arabian Sea

J1 (J’= H’/H max) (Pielou, 1969). Diversity and its components were computed using the program DIVER developed in C

The diversity index, evenness and species richness values for each site in relation to study period were computed; the results are given in Fig. 1. In 2005 the highest value of diversity index (H') was found at Sandspit (3.3189).The second highest species diversity was found at Clifton (3.1144) and the lowest value was recorded at Mubarak Village (2.5826). Species richness as measured by Menhinick’s index d 1 was highest at Keamari (2.861), second highest value was at Sandspit (2.835) and the lowest at Ibr ahim Haidry (1.867). Equitability was maximum at Sandspit (0.9758), second highest was at Paradise Point (0.9707) and the minimum at Ibrahim Haidry (0.8998) (Fig.1).

4 3 2 1 0

DIVERSITY INDEX (H)

Fig. 1. Nematode diversity index, Species richness and Evenness (2005)

In 2006 the highest value of diversity Index (H') was found at Sandspit which was 2.9647, followed by Korangi Creek where the diversity was found to be 2.8523 and the lowest value of diversity was at Mubarak Village (2.192). On the other hand, species richness d 1 was the highest at Sandspit (1.949). The second highest species richness was at Keamari (1.937) and the lowest value was recorded at Gadani (1.393). Equitability component was the highest at Sandspit (0.9732), the second highest value was Paradise Po int (0.9727) and the minimum at Ibrahim Haidry (0.836) (Fig.2). 4 Pakistan Journal of Marine Sciences, Vol. 20(1&2), 2011.

DIVERSITY INDEX (H)

Fig. 2. Nematode diversity index, Species richness and Evenness (2006) .

DIVERSITY INDEX (H)

Fig. 3. Nematode diversity index, Species richness and Evenness (2007) . Kazi et al.: Free-living marine nematodes from Arabian Sea 5

In 2007 again the maximum value of diversity Index (H') was found at Sandspit (2.9815). The second highest value was at Korangi Creek (2.852) and the lowest value of diversity was at Mubarak Village (2.289). Species richness d 1 was the highest at Paradise Point (2.1) and followed by Keamari (2.08) and the lowest value was recorded at Sonmiani (1.464). Equitability (e) was the highest at Korangi Creek (1.006). The second highest value was found at Hawksbay (0.9936) and the lowest at Ibrahim Haidry (0.9367) (Fig.3). The highest value of Shannon diversity (H’) index was at Sandspit and the lowest diversity was recorded at Mubarak Village in all observing years (2005-2007). In order to determine whether the species richness or equitability component was more important the general diversity (H`), multiple regression equation was developed. The equation relating general diversity (H`) to richness d 1 and evenness ‘e’ as under:

2 H`=0.594+1.55d 1+0.329J`R =0.4837

General diversity (H`) is explained 48.37% by the species richness and equitability components of which the major proportion of explained variance is contributed by species richness. Diversity indices incorporate both the species richness and evenness into a single value. Shannon index (H’) is the most popular and widely used index in community ecology. It is evident from the Figs. (1-3) that Sandspit exhibited the highest overall diversity index compared to other localities in all three years and Mubarak village recorded the overall lowest diversity in all years of observations. Of all the localities, Sandspit exhibited greater overall species richness and diversity. There are many environmental factors that affect species diversity. Some of these factors include seasonality, special heterogeneity, competition, predation, habitat type, environmental stability and productivity (Rosenzweig, 1995). The species richness index was highest in Keamari in 2005 and lowest at Gadani in 2006. The species richness index values in all localities were different in all the years. Evenness index was sensitive to species richness and it also considers even the rare taxa in the community. Considering all the localities, evenness showed highest values at Sandspit beach. This indicates that the nematodes were evenly distributed at Sandspit The present study clearly indicates that the Sandspit beach has a rich and varied nematode diversity by supporting the notion that the nematodes are the key components in all the ecosystems in which they live.

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