Evaluation of the contribution of Submarine Groundwater Discharge (SGD) to biological production of coastal fisheries resources by using stable isotope ratio recorded in the algae and the shell

2021 Fiscal Year Final Research Report

• Project/Area Number: 17K07889
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Aquatic bioproduction science
• Research Institution: Fukui Prefectural University
• Principal Investigator: Tominaga Osamu 福井県立大学, 海洋生物資源学部, 特命教授 (90264689)
• Project Period (FY): 2017-04-01 – 2022-03-31
• Keywords: 炭素安定同位体 / 窒素安定同位体 / 地下水 / 陸域・海域生態系 / 貝殻 / 海藻 / 生産構造

Outline of Final Research Achievements

We investigated two subjects 1) whether the δ13 C of ambient water reflect the proportion of freshwater flow rate in SGD, 2) whether the δ13C recorded in the shell of the sessile bivalve reflect that of the ambient water. There was a positive significant relationship between salinity and the δ13C of ambient water (p<0.01). The δ13 C of the shell was high at high SGD flow rate sites and the positive significant correlation was found between the δ13 C of the shell and that of ambient water. In order to estimate the proportion of freshwater flow rate in SGD from the δ13 C of the rock-oyster shell, we used the two end member mixing model including DIC concentration of both sea water and fresh underground water. The estimated average freshwater flow rate in SGD ranged from 4 % to 35%. These values are higher than those estimated from the δ13 C of ambient water. The difference of these results seems to be the difference of local SGD environment around rock-oyster.

Free Research Field

生産生態学

Academic Significance and Societal Importance of the Research Achievements

二枚貝貝殻中無機の炭素，酸素安定同位体を地下水トレーサーとして用いることで，地下圏を通した「陸域と沿岸域の生態系」，「環境と生物」の連関を客観的に可視化することが可能になった．この技術は，沿岸域の地下水環境マッピングへの応用のほか，貝殻切片から時間軸に添って微量な切削標本を採取することで，近過去に経験した環境を連続的に復元することを可能にする．過去のイベントと地下水環境を検証することにより，地下水が持つ生態学的意義をより明確にすることができ，沿岸域の生物生産機構の解明および沿岸域の総合管理に貢献すると考えられる．