9:00 AM - 9:15 AM
[MIS22-07] IODP Expedition 370: Temperature Limit of the Deep Biosphere off Muroto
Keywords:IODP, Deep Biosphere
Our primary objectives during Expedition 370 were to study the relationship between the deep subseafloor biosphere and temperature. We aimed to comprehensively study the factors that control biomass, activity, and diversity of microbial communities in a subseafloor environment where temperatures increase from ~2°C at the seafloor to ~120°C at the sediment/basement interface and thus likely encompasses the biotic–abiotic transition zone. We also aimed to determine geochemical, geophysical, and hydrogeological characteristics in sediment and the underlying basaltic basement and elucidate if the supply of fluids containing thermogenic and/or geogenic nutrient and energy substrates may support subseafloor microbial communities in the Nankai accretionary complex.
To address these primary scientific objectives and questions, we penetrated 1180 m and recovered 112 cores across the sediment/basalt interface. More than 13,000 samples were collected. Ensuring minimal contamination of potentially extremely low biomass core samples was of highest priority for the research objectives of Expedition 370. Therefore, rigorous quality assurance and quality control (QA/QC) efforts and super-clean technologies were implemented, including helicopter transport of freshly taken core samples to the onshore super-clean room facility at Kochi Core Center (KCC).