Realized distribution patterns and temporal change in ELSC animal communities

C.R. Fisher¹*, G.W. Luther III², E. Podowski¹, A. Madison², E. Becker¹, A. Sen¹, S. Ma², M. Yücel², A. Gartman², T. Moore², & C. Janzen³

Corresponding author: cfisher@psu.edu
¹The Pennsylvania State University, Department of Biology, University Park, PA 16802
²University of Delaware, College of Earth, Ocean and Environment, Lewes, DE, 19958
³Susquehanna University, Department of Chemistry, Selinsgrove, PA 17870

Abstract:
Our newest R2K relevant data addresses the relation between the megafauna on the Eastern Lau Spreading Center (ELSC) and their physical and chemical environment. Our results describe the chemical and thermal environments occupied by visible megafauna (their realized distribution) in 7 assessment sites on lava and 9 assessment sites on chimneys, spread over 4 vent fields along the ELSC. Because the relations among sulfide, temperature, and oxygen are different in different assessment sites, we are able to largely separate the effects of these parameters, which are strongly correlated within a site. Different symbiont-containing and sessile species occupy significantly different chemical and thermal regimes, and some of the more mobile fauna are specifically associated with a subset of these foundation fauna. Our data from 2006 also indicates different spatial structure in the diffuse fluid flow patterns associated with basaltic and andesitic lavas, and these are correlated with differences in the composition of the faunal communities on these substrates.

In 2009 we returned to all assessment sites established in 2005 and 2006 and collected data for re-analysis of the spatial structure of vent flow and the animal communities at each site in order to better understand temporal change. These data are still being analyzed, however, preliminary analyses support the successional pattern of change in the foundation species on lava that was hypothesized from our 2006 data and very stable “diffuse flow” communities on many of the larger and cooler chimneys analyzed. We have also just collected a large data set focusing on the effects of the symbiont-containing fauna on the dispersal and modification of diffuse fluids, and have conducted behavioral experiments in order to investigate biological interactions between the major faunal groups. I hope to have some preliminary analyses from these data sets as well.

Contributions to Integration and Synthesis:
With respect to synthesis with other studies on the ELSC, our data sets should be interpreted in the context of larger scale biological information (such as that collected with ABE and during the Tivey/Kim effort). In addition, the differences we find between assessment sites and vent fields are likely due to differences in the lavas as well as the chemical/thermal differences among sites. We have collected lava’s from all sites and hope to integrate petrological data into a larger scale look at differences in community structure on the ELSC. Similarly, understanding the stability in many of the chimney communities will require a better understanding of the longevity of diffuse flow venting on chimneys and the characteristics of the sulfide structures that allows this.

Our studies are also quite analogous to studies of community succession and associated processes conducted on chimneys on the JdFR (by Sarrazin, Juniper and co-workers) and on lavas on the EPR (by Shank, Mullineaux and co-workers). Our preliminary analyses suggest remarkable contrasts to the patterns of temporal change on chimney communities at these sites and clear similarities to patterns of temporal change on lavas on the EPR. Comparison to previously published and on-going studies at these sites may help to elucidate general patterns relating life history and physiology to ecological process in hydrothermal ecosystems and formulate hypotheses to test in other hydrothermal vent biogeographic provinces.