Estimation of the quantitative effect of sea cultivation aimed at dissapearnce of nutritional insufficiency at shallow water area

2023 Fiscal Year Final Research Report

• Project/Area Number: 20K04713
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22040:Hydroengineering-related
• Research Institution: Kagawa National College of Technology
• Principal Investigator: Yanagawa Ryoichi 香川高等専門学校, 建設環境工学科, 准教授 (70649095)
• Co-Investigator(Kenkyū-buntansha): 三好 真千 徳島文理大学, 理工学部, 講師 (40399168)
• Project Period (FY): 2020-04-01 – 2024-03-31
• Keywords: 海底耕耘 / 無機態窒素 / 貧栄養化

Outline of Final Research Achievements

Field experiments were conducted a total of six times and qualitative water quality changes due to cultivating activities could be captured. Specifically, an increase in ammonia concentration in the middle and bottom waters was detected, but the water mass with increased concentration did not reach to the surface layer by advection and diffusion. This was considered to be due to the fact that the extent and intensity of cultivating was insufficient for the size of the sea area, and that the cultivating was carried out at a time when vertical mixing was not sufficient. No clear trends in nitrate or nitrite elution could be detected, and it was considered difficult to clarify the quantitative cultivating effect in the field experiments. On the other hand, the development and implementation of an indoor forced-mixing experiment using sediment and water quality sampling has been initiated and will continue to be carried out in the future.

Free Research Field

沿岸生態系工学

Academic Significance and Societal Importance of the Research Achievements

植物の基礎生産に必要となる窒素・リン濃度が枯渇している海域でのノリ養殖事業を実現するため，水中栄養塩濃度の上昇を目的とした海底耕耘は，既存の栄養塩に富んだ底質を利用するという視点がこれまでに無かったこと，また海域生態系の物質循環機能を高める事も期待され，事業化に向けての社会的意義は高いと考えている．一方，本検討内では実施規模の小ささや定量的な効果を把握するに至らず，完了後も活動を継続して実用化に向けた取り組みを進めることとしたい．