9:35 AM - 9:50 AM
[MIS33-03] Evidence of microbial methane generation in the deep aquifer of accretionary prism in southern Okinawa Island, Japan
Keywords:accretionary prism, deep aquifer, methane production, fermentative bacteria, methanogenic archaea, syntrophic consortium
The groundwater and natural gas samples were collected from 4 deep wells constructed in southern Okinawa Island. The chemical analysis of the groundwater suggested that the deep aquifers are affected by seawater or seawater and rainwater. Analysis of the natural gas showed that methane is more than 93 vol% in all gas samples. Stable carbon isotopic analysis of methane in the natural gas and dissolved inorganic carbon (mainly bicarbonete) in the groundwater suggested that the methane was derieved from both thermogenic and biogenic origin. Analysis of 16S rRNA gene showed that the dominance of H2/CO2-producing fermentative bacteria and H2/CO2-using methanogenic archaea in the groundwater. Anaerobic cultivation targeting syntrophic consortium of the fermentative bacteria and the methanogenic archaea revealed high potential of microbialmethane generation was obserbed in all groundwater samples.
From these results, it was shown that the methane generation is conducted by syntrophic consortium of H2/CO2-producing fermentative bacteria and H2/CO2-using methanogenic archaea in the deep aquifer of accretionary prism in southern Okinawa Island. Furthermore, our results suggested that methane generation has been conducted by subterranean microbial community in deep aquifer of accretionary prism in wide range of the Pacific Ocean side of Southwest Japan.