Effects of habitat degradation on trophic structure of communities in mangrove estuaries

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K06101
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 39060:Conservation of biological resources-related
• Research Institution: Fisheries Research and Education Agency
• Principal Investigator: Nanjo Kusuto 国立研究開発法人水産研究・教育機構, 水産大学校, 講師 (70725126)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: マングローブ / 魚類生産 / 富栄養化 / 食物網

Outline of Final Research Achievements

The impact of habitat degradation on fish production structures in mangrove areas of natural and eutrophic rivers in the Yaeyama Islands, Okinawa Prefecture, was analyzed using carbon and nitrogen stable isotope techniques. In natural rivers, there were species utilizing marine particle organic matter, microphytobenthos (MPB)-derived organic matter, mangrove, and terrestrial particle organic matter. However, in eutrophic rivers, species that assimilate MPB were more abundant, and trophic flows derived from MPB were more dominant. Additionally, the nitrogen isotope ratios of food sources, prey, and fish were significantly higher than those in natural rivers, indicating that external nutrient inputs elevate the nitrogen isotope ratios across the entire food web.

Free Research Field

海洋生態学

Academic Significance and Societal Importance of the Research Achievements

本研究により，富栄養化は流入する栄養塩に迅速に応答する生産者による栄養フローを卓越させるだけでなく，食物網全体の窒素源になり替わることで魚類を含めた生物生産構造に影響を及ぼすことが示唆された。マングローブ域は富栄養化を含めた生息場の劣化が著しく進行している海域であるため，こうした人為的改変による生態系の応答に関する知見を蓄積することが，より効果的な保全策の確立につながると考えられる。