State of Nutrient Management by Analogy with the Changes in the Marine Environment in Osaka Bay over 44 Years

2022 Fiscal Year Final Research Report

• Project/Area Number: 16K16238
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Environmental policy and social systems
• Research Institution: Yamagata University (2022); Kyushu University (2019-2021); Nagoya Sangyo University (2017-2018); Kobe University (2016)
• Principal Investigator: Chika Suzuki 山形大学, 理学部, 教授 (40456702)
• Project Period (FY): 2016-04-01 – 2023-03-31
• Keywords: 赤潮 / 水質総量規制 / 重回帰 / 大阪湾 / 政策評価

Outline of Final Research Achievements

The relationship between the dynamics of red tide, one of the eutrophication phenomena, and the reduction of total phosphorus and total nitrogen inflow load has not been clear in some areas of Osaka Bay. Some regulated industries argue that regulating total nitrogen and total phosphorus in the effluent is unnecessary, and fisheries companies, such as those engaged in laver culture, have expressed concern about the reduction of nutrients in closed sea areas. Under the circumstances over the regulation of total nitrogen and total phosphorus, this study suggests that even during the period of fluctuation (FY2003/2004 to FY2016), the reduction of total nitrogen and total phosphorus inflow load still affected the dynamics of red tide in Osaka Bay. The "Nutrient Salts Management System" should be applied differently in the a-(イ) and b-（ロ）areas, prone to frequent red tides, and in the c-（ハ）area, where the emphasis is placed on laver culture.

Free Research Field

環境政策、STI政策評価

Academic Significance and Societal Importance of the Research Achievements

閉鎖性海域における富栄養化の問題は1970年代からわが国の水質保全政策上の課題であった。本研究は、これからまさに各自治体の努力で進んでいく「栄養塩管理制度」に基づく「栄養塩類管理計画」の策定や見直しに資する学術的な側面からのアプローチ（成果）となる。瀬戸内海環境保全基本計画の変更との同期がはかられる中での社会的意義は大きいと考えられる。兵庫県における栄養塩管理の方針は、栄養塩類の能動的運転管理に舵が切られる中で兵庫県と大阪府との調整に期待がもたれる。