The Pennsylvania State University The Graduate School Eberly College of Science COMMUNITY STRUCTURE OF HYDROTHERMAL VENTS AT THE EASTERN-LAU SPREADING CENTER A Thesis in Biology by Kevin A. Zelnio © 2009 Kevin A. Zelnio Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science August 2009 ii The thesis of Kevin A. Zelnio was reviewed and approved* by the following: Charles R. Fisher Professor of Biology and Assistant Department for Graduate Education Thesis Advisor Stephen W. Schaeffer Associate Professor of Biology Jay R. Stauffer, Jr. Distinguished Professor of Ichthyology Douglas Cavener Professor of Biology Head of the Department of Biology *Signatures are on file in the Graduate School iii ABSTRACT Deep sea hydrothermal vents form at plate boundaries and volcanic hotspots. Cold seawater seeping through fissures in the seafloor comes into contact with superheated rock above the magma chamber. The heated seawater rises carrying dissolved metals and sulfides that precipitate out of solution when it comes into contact with the cold water at seafloor’s surface, forming chimney-like structures. The Eastern-Lau Spreading Center (ELSC) in the Lau back-arc basin contains dense aggregations of chemoautotrophic macrofauna including two snails, Alviniconcha hessleri and Ifremeria nautilei, and the mussel, Bathymodiolus brevior. Each chemoautotrophic macrofaunal species occupies a defined thermo-chemical range. Alviniconcha hessleri is found in areas closest to the hydrothermal source where oxygen levels are lower, temperature is higher and sulfide concentrations are higher, whereas B. brevior occupies a microhabitat closer to the other end of the thermo-chemical spectrum. Ifremeria nautilei occupies a thermo-chemical tolerance range overlapping the upper and lower distributions of B. brevior and A. hessleri, respectively. In this study, 36 quantitative community samples from each of the chemoautotrophic macrofauna were collected from 4 sites with depths ranging from 1700 m in the south to 2800 m in the north. In general, communities associated with A. hessleri were lower in abundance and higher in Shannon diversity index and Pielou’s evenness index, yet had fewer numbers of species. Though Bray- Curtis similarity between I. nautilei and B. brevior hosted communities was significantly different (ANOSIM, Global R=0.82, P=0.02; Chapter 3: Table 6) there was a qualitative trend of higher abundance and biomass and lower Shannon diversity index, Pielous’s evenness index and mean number of species in collections of B. brevior relative to I. nautilei collections. There were distinct groups (ANOSIM: Global R=0.51, P=0.001; Chapter 3: see iv Table 6 for pairwise comparisons and Figure 6 for multidimensional scaling plot) of each community type in multi-dimensional space based on Bray-Curtis similarity. When grouped by study site, communities from southernmost Tu’i Malila had significantly higher Shannon diversity index, Pielou’s evenness index and mean number of species than the northernmost locality, Kilo Moana. In multi-dimensional space, only Tu’i Malila formed a distinct non- overlapping group based on Bray-Curtis Similarity while the two northern sites, Kilo Moana and TowCam, formed a distinct group and collections from ABE were interspersed. This thesis also contains taxonomic work on a new species of caridean shrimp (Chapter 1) and the hexacorallian fauna of the ELSC hydrothermal vents (Chapter 2). The new species of shrimp is in the family Alvinicarididae and genus Alvinocaris, a taxon specialized to deep-sea chemosynthetic ecosystems. A combination of morphological characters set it apart from known described species. Autapomorphies included a well- defined mesial notch in the telson and 2 rows of accessory spinules on the third to fifth pereopods. Analysis of the mitochondrial COI gene supports its position as a new species and confirms similar patterns within the family Alvinocarididae as found in previous molecular studies. A key to family Alvinocarididae is included. Additionally, 4 species of anemone, from the vicinity of hydrothermal vents at ELSC are described based on morphology. They are put into the genera Cyananthea, Alvinactis (Actinoscyphiidae), Chondrophellia (Hormathiidae) and Sagartiogeton (Sagartiidae). Two additional morphotypes from the families Actinostolidae and Hormatiidae could not be further identified based on existing material but contain notes on their morphology and distribution. The morphology and distribution of the first record of an abundant zoanthid from a hydrothermal vent is also noted, but not described. v TABLE OF CONTENTS List of Figures....................................................................................................................vii List of Tables................................................................................................................... xiii Acknowledgments........................................................................................................... xvi Introduction......................................................................................................................... 1 Chapter 1 A new species of Alvinocaris (Crustacea: Decapoda: Alvinocarididae) from hydrothermal vents at the East-Lau Spreading Center, Western Pacific.................. 10 Abstract..................................................................................................................10 Introduction........................................................................................................... 10 Materials and Methods.......................................................................................... 11 Taxonomic Results................................................................................................ 14 Ecology..................................................................................................... 26 Molecular Phylogeny................................................................................ 30 Discussion............................................................................................................. 32 Key to the Family Alvinocarididae....................................................................... 37 Acknowledgments................................................................................................. 42 Literature Cited..................................................................................................... 42 Chapter 2 Hexacorals (Anthozoa: Actiniaria, Zoanthidea) from hydrothermal vents in the South-western Pacific............................................................................................... 50 Abstract................................................................................................................. 50 Introduction........................................................................................................... 50 Materials and Methods.......................................................................................... 53 Results and Discussion......................................................................................... 54 vi Other Hexacorallia.................................................................................... 92 Ecological Observations........................................................................... 96 Acknowledgments................................................................................................100 Literature Cited................................................................................................... 100 Chapter 3 Community Structure of Hydrothermal Vent Communities at the East-Lau Spreading Center, Southwest Pacific.............................................................................. 107 Abstract................................................................................................................107 Introduction..........................................................................................................108 Materials and Methods........................................................................................ 110 Results................................................................................................................. 117 Discussion........................................................................................................... 130 Conclusions............................................................................................. 138 Acknowledgments............................................................................................... 139 Literature Cited................................................................................................... 140 Chapter 4 Biogeography of the Eastern-Lau Spreading Center......................................149 Literature Cited................................................................................................... 154 Appendix 1.......................................................................................................... 158 vii LIST OF FIGURES Figure 1-1: Map of collection sites at the Lau Basin with topographic features. Background image is courtesy of the Ridge Multibeam Synthesis Data Portal of the Marine Geoscience Data System............................................................................... 12 Figure 1-2: Figure 2: Alvinocaris komaii, new species, holotype female (a-d) and paratype female (e). a) whole specimen, right lateral view; b) rostrum,