Deep biosphere at the intersection of Itoigawa-Shizuoka Tectonic Line and Median Tectonic Line.

Abstract

Subsurface biosphere is one of largest biospheres on the Earth. However, most of geochemical processes driven by microbial activities in subsurface setting is still unknown. In this study, we focused on Suwa basin where active microbial methanogenesis is reported from deep subsurface. At the intersection of Itoigawa-Shizuoka Tectonic Line (ISTL) and Median Tectonic Line (MTL), Suwa basin is composed of organic-rich sedimentary layers. There are active faults and hot springs within the complex hydrogeological structure of the basin on the boundary of North American Plate and Eurasian Plate. These geological backgrounds would host the potential of microbial ecosystems with diverse community structures and functional properties in the deep subsurface. In this study, we collected groundwater samples from seven hot springs (max. 1000 meter below ground level) and three monitoring wells (max. 100 mbgl). Using these samples, we reveal microbial community structure with quantifying biomass ratio of bacteria and archaea based on membrane lipid analysis.