Deep Hot Biosphere Targeted Locus (Loci)

The IODP Expedition 331 to the Okinawa backarc basin provided a unique opportunity to study the deep, hot subvent biosphere— the subsurface environment surrounding an active vent hypothesized to host an active microbial ecosystem despite the high temperature hydrothermal conditions. Hydrothermal vent systems at tectonic settings and backarc basins have extremely high fluxes of energy and matter, and are characterized by the emission of thermally charged fluid rich in H2, CO2, sulfide, and other reduced compounds. Many studies have examined anaerobic microbial processes that thrive within the high-temperature discharge that comes in contact with surrounding seawater. However, the sedimentary subsurface surrounding an active vent contains a unique geochemistry due to the lateral migration of hydrothermal fluid. Such conditions in the marine subsurface have not been thoroughly studied even though the deep, hot, sedimentary subsurface has the potential to host a diverse microbial ecosystem.