Fire and famine: Controls on microbial activity in the deep hydrothermal subsurface of the Guaymas Basin



Up to 33 percent of the Earth’s total living biomass is estimated to be within the marine subsurface, but the activity of these extremophiles, and their role in biogeochemical cycling, is largely unknown. The Guaymas Basin, Mexico, is characterized by active rifting producing steep geothermal gradients and dynamic geochemical environments. Preliminary results indicate cells are detectable down to ~300 meters below the seafloor and at in situ temperatures up to 90ºC, but the activity of these microorganisms remains a mystery. We propose to use stable isotope incubations to quantify single-cell anabolic activity and investigate how temperature and energy availability control activity. This study will improve our understanding of the energetic and thermal limits of life in the hydrothermal deep marine biosphere.



Microorganisms play a fundamental role in cycling carbon and nitrogen, and in shaping our planet’s habitability. I investigate the links between marine sediment microorganisms and their environments, and thus I’m pursuing a Ph.D. at Stanford University in Anne Dekas’ group. Using microcosm experiments and stable isotope techniques, I track the activity of subseafloor archaea and bacteria and investigate their physicochemical controls. In particular, the Guaymas Basin deep subsurface is an ideal site to explore the role of microorganisms in cycling climate-warming methane. Sailing on IODP Expedition 385 was an amazing experience; I met wonderful colleagues from all around the world, was at sea for two months, and was challenged to think in an interdisciplinary fashion. I’m excited to pursue my research through the Schlanger Fellowship and am eager to see what we discover in Guaymas Basin’s deep subsurface.