Bioenergetics of the subseafloor biosphere; implications for life on terrestrial planets

by Arthur Spivack (University of Rhode Island)

Monday 3 Oct 2011, 10:00 → 10:45 Europe/Stockholm

DeGeersalen, Earth Sciences Building, Y level 2, Stockholm University Frescati Campus

Major questions in subsurface biosphere research are related to bioenergetics. Specific questions that place fundamental constraints on habitability are: How much energy is required to support a given amount of biomass? And what is the minimum energy yield of reactions that are biologically utilized? Beyond the two questions described above, there are related issues, such as, the energetic rules that govern the distribution of subsurface life. In particular, the controls on the distribution and rates of the various energy producing metabolic reactions and the possibility that some buried marine ecosystems rely on radiolytic hydrogen as their principle electron donor. To answer this questions, in situ metabolic rates and energy yields of diverse microbial activities in deep sediments of the eastern equatorial Pacific have been determined based on sedimentary pore fluid chemical profiles. The inferred maintenance energies to support these sub-seafloor communities are orders of magnitude lower than what was previously thought to be needed to support life. Additionally, based on this maintenance energy, hydrogen produced by radiolysis in typical marine sediments could support approximately 105 cells/cm3 while approximately 104 cells/cm3 could be supported in a water-saturated sediment Martian crust.