2021 Fiscal Year Final Research Report

Hypoxia-driven acidification of enclosed bay: evaluating CO2 production by microbial respiration and the impacts on marine organisms.

Research Project

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Project/Area Number	17H03854
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Research Field	Aquatic bioproduction science
Research Institution	Nagasaki University
Principal Investigator	WADA MINORU 長崎大学, 水産・環境科学総合研究科(水産), 教授 (70292860)
Co-Investigator(Kenkyū-buntansha)	石松惇長崎大学, 海洋未来イノベーション機構, 名誉教授 (00184565) 鈴木利一長崎大学, 水産・環境科学総合研究科(水産), 教授 (20284713) 松下吉樹長崎大学, 水産・環境科学総合研究科(水産), 教授 (30372072) 嶋永元裕熊本大学, くまもと水循環・減災研究教育センター, 教授 (70345057)
Project Period (FY)	2017-04-01 – 2021-03-31
Keywords	季節性貧酸素 / 酸性化 / 呼吸 / 閉鎖性内湾 / 化学合成独立栄養細菌
Outline of Final Research Achievements	In Omura Bay, Nagasaki Prefecture, it is known that dissolved oxygen levels drop from late June each year, and by mid-August the bay is temporarily anoxic. Furthermore, it has been demonstrated that the bay is acidifying at the same time. It was also found that as anoxia progresses, the aragonite saturation of the water near the seafloor drops to about 1.0, which may inhibit the formation of bivalves and other shellfish species. On the other hand, when anoxic conditions were temporarily eliminated by the passage of a typhoon in August and September and returned to anoxic conditions again, the water did not become acidified in step with the decrease in DO. We found that chemosynthetic autotrophs that simultaneously consume DO and CO2 may be involved in the formation of bottom water masses under such conditions.
Free Research Field	水圏微生物学
Academic Significance and Societal Importance of the Research Achievements	国内外を問わず多くの閉鎖的な内湾は貧酸素化することが知られているが、本研究で示したように、それらの海域でも貧酸素化と酸性化が同時に生じている可能性が高く、水産資源の保全の観点から貧酸素と酸性化を同時に監視することの必要性が明確となった。一方、本研究で、化学合成独立栄養細菌の働きによって、貧酸素状態での酸性化が緩和される可能性を始めて示し、化学合成独立栄養細菌の生態学的役割に関する新たな視点を提供した。