Investigating the universality of triggers for blue-green algae caused by rainfall

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K20466
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 64010:Environmental load and risk assessment-related
• Research Institution: Shimane University
• Principal Investigator: Shingo Masuki 島根大学, エスチュアリー研究センター, 客員研究員 (80806894)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: アオコ / ダム湖 / 藍藻 / アオコ対策技術

Outline of Final Research Achievements

It was reported that the oligotrophic layer formed in the dam lake is a factor that suppresses blue-green algae, and that the oligotrophic layer is eliminated by rainfall above a certain scale is a factor that causes blue-green algae (Masuki et al.). , 2018, JSCE Water Engineering Proceedings). In this study, we investigated the universality of these phenomena. As a result, it was confirmed that in the dam lake, which is a eutrophic lake, the surface layer at a depth of 0.5 to 2 m becomes oligotrophic in summer. It was also confirmed that the blue-green algae started to grow about 10 days after the large-scale rainfall. On the other hand, when the phosphorus-restricted state continued even after the stratification was destroyed, the state of abnormal growth of blue-green algae (blue-green algae) was not reached. It was suggested that the nutrient characteristics of the inflow water may affect the development of blue-green algae.

Free Research Field

自然環境科学

Academic Significance and Societal Importance of the Research Achievements

アオコは景観を悪化させ、悪臭を放ち、水源利用する場合には飲用水にカビ臭を生じさせ，毒素による人への健康被害も報告されている。また，下流域の生態系に悪影響を及ぼす可能性もあり，アオコの低減化に関する研究および技術開発は極めて重要である。
アオコの発生メカニズムは、未だ十分に理解されておらず、現在も様々な研究が続いている。本研究では、既報の「ダム湖の表層貧栄養層の形成がアオコの抑制に繋がること」、そして、「降雨による攪乱作用により表層貧栄養層が解消されることがアオコの発生トリガー」であることの2点について、他ダムを選定し、その普遍性を調べた。より効果的なアオコ対策へと繋がることが期待される。