90% of the carbon that makes up the earth is occupied by the core, mantle, and crust inside the earth, and the rest is distributed to the surface ocean, atmosphere, and biosphere.
The carbon on the surface is carried into the earth by the subduction zone of the plate, but a part of it becomes carbon dioxide during the subduction, and it is released as volcano or hot water and supplied to the surface again.This time, international collaborative research teams such as Tokyo Institute of Technology and Oxford University have confirmed that this process is affected by microbial activity and that the amount of carbon supplied from the subduction zone to the forearc region (the region between the volcanic arcs). It was clarified that the value is two orders of magnitude larger than the previous estimates.
To elucidate the carbon cycle and related processes, the project "Biology Meets Subduction" of the international joint research institute "Deep Carbon Observatory" is a hot spring in Costa Rica, a country of volcanic arcs formed by subduction of ocean plates.・ A spout survey was conducted.
Analysis from the isotope ratios of helium and carbon dioxide, the isotope ratios of dissolved inorganic and organic carbon, etc. in the collected hot spring water and ejected gas shows that about 90 of the carbon dioxide supplied from the subduction zone to the forearc region. It was found that% is combined with carbon dioxide in the crust to form carbonate, and is further carbon-fixed by microorganisms to become organic carbon and dissolved in hot spring water.
Until now, the effects of biological activity have not been considered in the process of carbon supply from the subduction zone to the surface layer, but this analysis has shown for the first time that there is an effect of carbon fixation of microorganisms.
In the new carbon cycle model including microbial activity, the amount of carbon supplied to the forearc region will be two orders of magnitude larger than previously estimated.This means that the amount of carbon returning to the mantle in the subduction zone is significantly smaller than previously estimated.
This new discovery is believed to lead to a reassessment of the global carbon balance.
Paper information:[Nature] Forearc carbon sink reduces long-term volatile recycling into the mantle
