### History of the Model Projects for Improving the Aquatic Environment in Enclosed Seas – Miyagi, Osaka, and Hyogo Prefectures – April 2007 to the 2020s

### History of the Model Projects for Improving the Aquatic Environment in Enclosed Seas – Miyagi, Osaka, and Hyogo Prefectures – April 2007 to the 2020s #### 2007: Launch of the Model Projects Model projects aimed at improving the aquatic environment in enclosed seas were launched in Miyagi, Osaka, and Hyogo Prefectures. Targeting the Sendai Bay, Osaka Bay, and Harima Sea, these projects aimed to resolve local water pollution and achieve the sustainable conservation of ecosystems. Technologies to reduce wastewater from aquaculture and suppress nitrogen and phosphorus emissions were introduced, improving oxygen deficiency in coastal areas. Through collaboration among local governments, businesses, and research institutions, and through demonstration experiments, the projects achieved results that balanced the reduction of environmental impact with the revitalization of the local economy. #### 2010s: Expansion of Application Scope In the 2010s, the scope of technology application expanded across the target regions, and the project’s effects became more pronounced. In the Sendai Bay area, new technologies were introduced to promote the decomposition of organic matter discharged from aquaculture, reducing annual nitrogen emissions by 15%. In Osaka Bay, the area of artificial tidal flats and seaweed beds was expanded to 100 hectares, resulting in a more than 20% increase in the number of fish and crustacean species inhabiting the area. In the Harima Sea, wastewater treatment facilities were upgraded, improving water clarity in coastal areas and contributing to the revival of the tourism industry. Furthermore, as part of nationwide environmental policies, each prefecture formulated a “Wide-Area Water Environment Improvement Plan.” This allowed for more unified progress in efforts to improve the entire enclosed sea area. #### 2020s: Current Status and Progress **Miyagi Prefecture (Sendai Bay)** In the 2020s, the Sendai Bay Project led by Miyagi Prefecture made further progress. In collaboration with aquaculture operators, the project worked to reduce wastewater discharge from aquaculture farms and improve water quality, resulting in a 25% reduction in annual nitrogen and phosphorus emissions compared to 2007 levels. Furthermore, a new water purification method utilizing microorganisms was adopted, significantly improving oxygen concentrations in coastal areas. **Osaka Prefecture (Osaka Bay)** In Osaka Bay, the “Rich Osaka Bay” project continues to be promoted. The installation of artificial seaweed beds and tidal flats has expanded, leading to improvements in coastal seabed conditions. Furthermore, by utilizing seabed improvement materials independently developed by companies, fishery resources have recovered, and in 2022, the catch volume within the bay increased by 10% compared to the previous year. **Hyogo Prefecture (Harima Sea)** In the Harima Sea, Hyogo Prefecture and local companies are collaborating to conserve coastal vegetation and implement advanced treatment of industrial wastewater. By 2020, the area of vegetation zones reached 300 hectares, leading to improved ecosystem diversity. Furthermore, as a result of these environmental conservation efforts, the number of tourists has increased by 20% compared to 2015. #### Future Outlook These initiatives are contributing to the revitalization of the local economy and the promotion of tourism, and there are expectations that the technology will be applied to other regions with enclosed coastal waters. In particular, under the Japanese government’s “Comprehensive Plan for Marine Environmental Measures,” the goal is to achieve further technological innovation and improve the aquatic environment through collaboration with local residents. The achievements in Sendai Bay, Osaka Bay, and the Harima Sea will continue to attract attention both domestically and internationally as important model cases for realizing a sustainable society.