N-150. Using 454 Tag Sequencing to Determine the Diversity and Distribution of Subseafloor Indicator Organisms at Deep-Sea Hydrothermal Seamounts of the Pacific Ocean

J. A. Huber1, D. A. Butterfield2, P. R. Neal1, S. M. Huse1, D. B. Mark Welch1, H. G. Morrison1, M. L. Sogin1;
1Marine Biological Lab., Woods Hole, MA, 2Univ. of Washington, Seattle, WA.

Crustal mixing of reduced hydrothermal fluids with oxygen-replete seawater creates subseafloor habitats that span gradients in temperature, energy availability, and physical parameters. However, our knowledge of what microbes are present and how they are distributed in this dynamic geochemical environment is fragmentary. We used a tag sequencing strategy that combines the use of amplicons of the V6 hypervariable region of SSU rRNA with massively parallel sequencing to determine and compare the diversity, distribution, and relative abundance of subseafloor indicator organisms in diffuse flow vents at hydrothermal seamounts across the Pacific Ocean (Axial, Loihi, and Mariana Arc). Key groups identified include the archaeal genera Methanothermococcus, Archaeoglobus, and Thermococcus and the bacterial class epsilon-proteobacteria. Cluster and non-metric multidimensional scaling analyses of these groups does not show distribution patterns tied to specific volcanoes. Instead, vents with unique chemistries appear to host distinctive microbial communities. For example, vent fluids from Champagne at NW Eifuku are predicted to pass through a liquid and/or hydrate CO2 layer, and these fluids host a unique community of archaea, including members of the Desulfurococcaceae and Thermococcaceae families. Other sites of note include Axial vent Marker 113, which hosts a large Methanothermococcus community and has extremely high gas content relative to temperature, as well as Loihi vent Upper Hiolo Ridge, where Archaeoglobus dominates, and fluids contain high levels of Fe(II) with minimal hydrogen sulfide. While four genera of epsilon-proteobacteria (Sulfurovum, Arcobacter, Sulfurimonas, and Thioreductor) were found at every vent sampled at Axial and Mariana Arc, these were virtually absent from Loihi Seamount, which instead hosted a distinct community of the genera Hydrogenimonas and Natratiruptor. Thus, the tag sequencing approach reveals differences in diversity and community structure that correlate with major differences in environmental chemistry, distinguishing iron-dominated, sulfidic, and CO2-dominated submarine hydrothermal habitats.