Environmental change and material circulation in the shallow estuary: Accompanied by the opening of new airport in Ishigaki island.

2018 Fiscal Year Final Research Report

• Project/Area Number: 25820229
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Hydraulic engineering
• Research Institution: Tokai University
• Principal Investigator: TERADA Kazumi 東海大学, 工学部, 准教授 (30547998)
• Project Period (FY): 2013-04-01 – 2019-03-31
• Keywords: マングローブ / サンゴ / 海草藻場 / 生息調査 / 栄養塩 / 流動 / マイクロプラスチック / 地下水

Outline of Final Research Achievements

For the conservation and sustainable use of mangroves, seagrass beds and coral reef on Ishigaki Island, the changes in the sightseeing population and land uses and the distribution of seagrass and coral reef were monitored. Tidal change of water qualities such as Dissolved Oxygen, Nitrogen, Phosphorus and Suspended Solids were also measured. Since the opening of the new Ishigaki Airport in 2013, the number of passengers entering the area increased approximately 1.7 times, and the construction area increased on the southern area. Monitoring results of corals and seagrass beds made it possible to clarify the state of large-scale coral bleaching in 2016, as well as the state of recovery thereafter. Water qualities and nutrient fluxes in the Fukido mangrove estuary indicated that the mangrove estuary played a mitigating role in the exchange of sediments and nutrients between terrestrial and oceanic environments.

Free Research Field

海岸工学、水環境工学

Academic Significance and Societal Importance of the Research Achievements

サンゴ、海草の生息分布は環境省を始め国内外で定期的に行われているものの、本調査のように細かいメッシュで季節ごとに調査した事例は少なく、地元観光業者への情報提供ならびにサンゴ、海草の生態理解の一助となったと考えられる。またマングローブ河川の水質挙動、物質輸送量の一端が明らかになったが、陸域からの土砂、窒素、リン等の流出負荷量を把握することは隣接する海草藻場、サンゴ礁の保護へと繋がるものと考えられる。また本調査により初めて吹通川マングローブ林内にもマイクロプラスチックが存在することが確認され、世界的に問題となっているプラスチック汚染の一端を明らかにすることができた。