Study of methane metabolic cycle of microorganisms in marine sediment core using natural level radiocarbon analysis

点击翻译按钮获取中文摘要

This research was executed to develop various evaluation techniques for clarifying biomarker signals and their signal strength left for marine sediments concerning about methane hydrate, whether these signal had been newly generated by living microorganisms in the sediment or they were methane origin carbon on the site. At first, a graphitization technique for making precise and accurate radiocarbon measurements on small samples containing less than 100 μg of carbon was developed. The development of a microscale radiocarbon analysis technique is very important for advanced research in various fields of study, especially organic geochemistry. Using this method, the piston cores from the continental slope sediments in the Oyashio current region, which recently is found to bear immense amounts of methane hydrate, have been investigated about planktonic and benthic foraminiferal carbon isotope records during the past 34 kyr. Moreover, in order to investigate relation with foraminifera carbon isotopic signal and methane release from the seafloor, biomarker compositions and their carbon isotope have been analyzed in the light of the past activity of methanotrophic bacteria in the oxic-anoxic interface in the overlying water column and/or surface sediment. To analysis for microbial communities and microbial RNA in marine sediment core, we modified and developed DNA/RNA simultaneous extraction method using the Mutsu-bay sediments. We identified several partial sequences of 16S rDNA related to methanogens and methanotrophs in the sediment cores.