报告题目：Activities and Productivity of the Sub-Seafloor Biosphere at Deep-Sea Hydrothermal Vents
报 告 人：Stefan Sievert Associate Scientist
联 系 人：王风平 email@example.com
Despite 40 years of research, knowledge of in situ metabolism of microbes carrying out carbon fixation in marine hydrothermal systems is still very limited. Particularly lacking are studies identifying the chemosynthetically active microbes and measuring rates of CO2 fixation in situ. Here, we present data from innovative incubation approaches for assessing chemoautotrophic production in deep-sea vent systems. We quantified chemosynthetic primary productivity of natural microbial communities sampled from Crab Spa (9ºN East Pacific Rise) during incubations that maintained seafloor pressure and temperature. During these experiments, we measured carbon fixation, microbially-catalyzed inorganic redox reactions, and community composition, providing insight into both the identity and activity of natural populations under environmentally-relevant conditions. This allowed us to determine growth efficiencies for natural communities, providing constraints on potential magnitude of chemosynthetic primary productivity and the residence time of the sub-seafloor biosphere below Crab Spa. Combining this information with results from ‘omic’ approaches, reveals a highly active microbial community dominated by diverse Campylobacteria carrying out carbon fixation predominantly fueled by the oxidation of sulfide with nitrate and oxygen. The microbial communities are characterized by functional redundancy, meaning that different taxa appear to perform similar functions using homologous pathways, but being optimally adapted to the thermal and redox gradients existing in the sub-seafloor along the flow path of the mixing fluids. Overall, our data provide a comprehensive view of the sub-seafloor biosphere underlying this vent site and its biogeochemical significance for the surrounding deep ocean.