Sen

A first look at temporal changes in megafaunal communities on the Eastern Lau Spreading Center: June 2006-June 2009

A. Sen¹, E.L. Podowski¹, E.L. Becker¹, G.W. Luther III², & C.R. Fisher¹

¹Biology Department, Pennsylvania State University, 208 Mueller Lab, University Park, PA 16802
²College of Marine and Earth Studies, University of Delaware, 700 Pilottown Rd., Lewes, DE 19958

Abstract:
Previous in situ and laboratory studies clearly indicated that the three dominant taxa of symbiont-containing megafauna in the Eastern Lau Spreading Center have different physiological tolerances and requirements, and these contribute to realized distributions in habitats with different chemical and thermal characteristics. These physiological differences, combined with differences in their life histories and biological interactions, may determine the relative success of each taxon as conditions change over time in different hydrothermal vent habitats and communities. Based on an analysis of data from 2005 and 2006 cruises to these sites, we had hypothesized that Alviniconcha hessleri was a pioneer megafaunal species which would later be joined and eventually replaced by Ifremeria nautilei and Bathymodiolous brevior. By analogy with the East Pacific Rise B. thermophilus, we hypothesized that B. brevior could replace the snails over time in many microhabitats and would persist the longest as sites aged and flow declined. In 2006, we also noted that aggregations of large snails and mussels were often present on chimneys and hypothesized that these communities might be less ephemeral than chimney communities on the East Pacific Rise or the Juan de Fuca Ridge.

In June 2009, we revisited 7 diffuse flow communities and 8 chimney communities that were imaged and intensively surveyed chemically and thermally in 2006. At each of these sites we have constructed photomosaics from the images collected in 2009 and have begun to analyze the chemical and temperature data for some of the sites. Here, we present some of the highlights from a preliminary examination of the new data sets.