Elucidating the contribution of terrestrially derived organic matter to organic carbon sequestration in the coastal ocean

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05748
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 40030:Aquatic bioproduction science-related
• Research Institution: Nagasaki University
• Principal Investigator: Takasu Hiroyuki 長崎大学, 水産・環境科学総合研究科(環境), 准教授 (00774803)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 溶存態有機物 / 炭素貯留

Outline of Final Research Achievements

We compared the natural carbon stable isotope ratio (δ13C) values of DOC at the beginning and end of an incubation experiment to evaluate the bioavailability of riverine DOC from the northern Ariake Sea. The δ13C values of DOC at the beginning and end of an incubation experiment implied that the decomposed DOC in incubation bottles must be mainly derived from terrestrial sources. In addition, DOM enrichment bioassays were conducted to test whether the growth of phytoplankton in Isahaya Bay can be stimulated through the addition of terrestrial DOM. Microsized phytoplankton (> 10 μm) growth rates in both the presence and absence of antibiotics, a bacterial inhibitor, were stimulated by DOM addition. The results suggest that terrestrial DOM is partly removed by bacteria and phytoplankton in coastal waters.

Free Research Field

生物地球化学、海洋生物環境学

Academic Significance and Societal Importance of the Research Achievements

陸起源有機物が沿岸域において速やかに分解される場合は、海域における二酸化炭素放出量の増加につながり、一方で分解されない場合は、沿岸域における炭素貯留量の増加につながる。このように、陸起源有機物の分解性は、海洋の炭素貯留量を左右し、ひいては気候変動に影響を及ぼし得る。そのため、陸起源溶存態有機物の運命を明らかにすることは、海洋の炭素隔離機構の解明にとどまらず、将来的な気候変動予測においても極めて重要である。本研究は、不明な点が多い陸域起源有機物の分解性やその除去プロセスの一端を明らかにしたものであり、気候変動予測に資する情報である。