Investigation into the Impact of Red Soil Runoff on Biological Habitats in Okinawa Prefecture Using Underwater Sounds of Marine Organisms

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K12196
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 63040:Environmental impact assessment-related
• Research Institution: Akashi National College of Technology
• Principal Investigator: Watanabe Moriyoshi 明石工業高等専門学校, 都市システム工学科, 教授 (00390477)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 海中発音生物 / テッポウエビ類 / 赤土等流出 / 環境評価 / モニタリング調査

Outline of Final Research Achievements

OKINAWA’s red soils runoff adversely affects the sea environment and aquatic animals. This study unravel OKINAWA's red soils runoff adversely affects to aquatic animals using underwater sounds. Our laboratory has been conducted sea environment assessment method using the pronunciation of snapping shrimp, which is known as an underwater-sounding organism. In this study, "pulse count" is used as a biological indicator. The pulse count is number of a shrimp makes a sound per minute, and can be measured in a short time using a hydrophone.
We set up survey points as high red soils runoff points and control points, and conduct periodic surveys of these points, and estimated the effects of red soil from periodic change of pulse count. Pulse count in control points increased during periods of high-water temperature, but high red soil runoff points decreased, so it is expected that this method will be able to evaluate the biological effects of red soils runoff.

Free Research Field

土木工学、環境工学

Academic Significance and Societal Importance of the Research Achievements

沖縄県赤土等防止流出防止対策基本計画の調査結果概要では、海域の評価は赤土等堆積状況からの実施が基本であり、調査頻度の少なさから生物生息状況の評価は補足的な位置づけとなると指摘している。本研究では、測定困難な海中の生物の生息状況や活性度を、生物の発する音を利用して測定する手法を用いることにより、赤土等流出が生物の生息状況に及ぼす影響を検出することができた。本研究の成果を用いれれば、生物への悪影響のみならず環境保全対策の効果や沿岸開発事業を評価することができるようになる。