Interdisciplinary Studies of Biological Community Structure at Deep-Sea Hydrothermal Vents along the East Pacific Rise

R.A. Lutz¹, T.M. Shank², G.W. Luther³, & C. Vetriani¹

Corresponding author: rlutz@marine.rutgers.edu
¹Institute of Marine and Coastal Sciences, Rutgers University, New Brunswick, NJ 08901
²Biology Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543
³College of Marine Studies, University of Delaware, Lewes, DE 19958

Abstract:
Studies conducted at 9°50’N along the East Pacific Rise (EPR) between 2004 and 2007 suggest the following. (1) The presence of extensive numbers of mussels within selected regions of the vent faunal assemblage inhibits the colonization and subsequent growth of vestimentiferan tubeworms through depletion of H2S below critical levels. (2) If mussels are removed and subsequently excluded from regions with elevated temperatures and H2S concentrations within a mussel population at an active vent site along the EPR, then the area will be colonized by numerous vent-endemic species, including Tevnia jerichonana and Riftia pachyptila, that reportedly represent ‘‘early vent colonizers’’. (3) During later stages of succession, as H2S levels are reduced by the overlying mussel population, the vestimentiferan Oasisia alvinae remains as the last (‘‘climax’’) vestimentiferan in and among the mussel population. (4) Seismic events will alter the chemistry and temperatures of diffuse hydrothermal vent fluids within the region. (5) Specific bacteria are repeatedly found in newly-established microbial filamentous communities from different diffuse flow vents within the general area of 9°50’N along the EPR – in particular, Halothiobacillus sp. was consistently found as part of the filamentous microbial community on experimental basaltic recruitment blocks and on pieces of equipment left in nearby vent areas, as well as on natural substrates in adjacent vent fields, suggesting that these microorganisms may serve as newly-formed biofilms associated with diffuse flows. (6) Mesophilic facultative and obligate autotrophic microorganisms are important components of the microbial assemblages in diffuse vent flows and associated thermal plumes - the isolation of obligatively autotrophic Thiomicrospira spp. and facultatively autotrophic Halomonas spp. from 10–3 and 10–4 dilutions of the hydrothermal fluids at the Marker 119 site (and from even higher dilutions in fluids collected at other nearby vents in the region) indicates that both these species are abundant (and likely relevant) constituents of the microbial communities that inhabit diffuse flow vents along the EPR.

Contributions to Integration and Synthesis:
The 9°50’ N area along the EPR has been extensively studied by large numbers of multi-disciplinary groups of scientists since a volcanic eruption that occurred within this region in April, 1991. Integration of our own extensive biological, geochemical, temperature and seismic datasets with those datasets obtained by these other investigators should provide invaluable insights into our understanding of basic underlying processes controlling vent dynamics and biological community structure. Our own studies have revealed much about mechanisms of dispersal, recruitment, and organism-chemical interactions, all of which can theoretically be woven into potentially wonderful models and “syntheses” when combined with the collective studies of those other researchers who have worked within this region.