海底下の微生物起源ガスと生命活動との関わり

－海洋科学掘削の最前線－

抄録

Scientific ocean drilling has a history of about half a century, which has so far brought remarkable discoveries in Earth Science, such as demonstration of plate tectonics and drastic environmental changes that occurred in the past on our planet. Among them, the substantial expansion of our knowledge on the discovery of “deep subseafloor biosphere” is one of the milestone scientific achievements that overturned the paradigm of the habitability in Earthʼs interior. To date, numerous multidisciplinary studies of sediment samples cored from subseafloor have demonstrated that a remarkable number of physiologically and thus functionary unknown microorganisms are predominant, which have indigenously evolved under the dark subsurface biosphere. On-going effort on scientific exploration of the deep biosphere shows that functionality of the deep microbial ecosystem lurking inside of the Earth indeed plays important ecological roles in the global carbon and other elemental cycling; e.g., degradation processes of the buried organic matter, formation processes of biogenic gas including methane hydrates in the global subseafloor sedimentary environments. In this lecture, we introduce the recent scientific knowledge on the interaction between the occurrence of biogenic gas and the deepbiosphere activity, and discuss how we could develop carbon and energy circulation systems for the sustainable human society and Earthʼs environment in the future.