Sclerosponge as archive of pCO2 in the past oceans

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K17669
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Environmental dynamic analysis; Geochemistry/Cosmochemistry
• Research Institution: The University of Tokyo
• Principal Investigator: Kentaro Tanaka 東京大学, 大気海洋研究所, 特任研究員 (20792766)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 古環境 / 炭酸カルシウム / 海洋酸性化 / 硬骨海綿 / 二酸化炭素

Outline of Final Research Achievements

Sclerosponges produce calcareous skeletons. In this study, we examined whether the chemical composition of sclerosponge skeletons (boron concentration and isotope ratios) reflects seawater pH and carbonate ion concentration. As a result, pH estimated from the boron isotope ratio was nearly consistent with seawater pH, suggesting that sclerosponge can be utilized as a new archive of seawater pH. However, the carbonate ion concentration estimated by boron concentration and isotope ratios was higher than seawater value, indicating that it is difficult to estimate carbonate ion concentration based on sclerosponges.

Free Research Field

地球化学

Academic Significance and Societal Importance of the Research Achievements

本研究では硬骨海綿のホウ素同位体比が海水pHの指標となりうることを示した．これまでもサンゴの骨格や有孔虫に記録された化学組成を利用して海水のpHを推定する研究が行われてきた．しかし，サンゴ骨格の化学組成から推定されるpHは海水のｐHより高く，有孔虫を使った研究が行われた海域は限られている．今回の成果によってこれまでより広い海域と年代のpHをより正確に推定できる可能性を提示できた．本研究の成果をもとに全球規模での大気―海洋間の二酸化炭素の収支をより正確に明らかにする試みが促進されると期待できる．