[A-HW22] 流域生態系における物質輸送と循環：源流から沿岸まで

[AHW22-05] 沿岸域の底質に吸着したリン酸塩はサンゴ稚ポリプの骨格形成を阻害する

*飯島 真理子¹、安元 純²、井口 亮¹、中村 崇³、酒井 一彦⁴、廣瀬 美奈⁵、安元 加奈未⁶、水澤 奈々美⁷、鈴木 淳¹、神保 充⁷、渡部 終五⁷、安元 剛⁷ (1.国立研究開発法人　産業技術総合研究所、2.琉球大学農学部、3.琉球大学理学部、4.琉球大学熱帯生物圏研究センター、5.トロピカルテクノプラス、6.東京理科大学薬学部、7.北里大学海洋生命科学部)

キーワード：リン酸塩、石灰化、底質、サンゴ

To test the hypothesis that terrestrial runoff affects the functions of calcareous sediments in coral reefs and hampers the development of corals, we analysed calcareous sediments with different levels of bound phosphate, collected from reef areas of Okinawajima, Japan. We confirmed that phosphate bound to calcareous sediments was readily released into ambient seawater, resulting in much higher concentrations of phosphorous in seawater from heavily polluted areas (4.3 to 19.0 µM as compared with < 0.096 μM in natural ambient seawater). Additionally, we examined the effect of phosphate released from calcareous sediments on the development of Acropora digitifera coral juveniles. We found that high phosphate concentrations in seawater clearly inhibit skeletal formation of coral juveniles. The present study demonstrated that terrestrial phosphate is bound to calcareous sediments in coastal areas and the bound phosphate is readily released into ambient seawater, resulting in high concentrations of phosphorous in surrounding seawater. These high phosphate concentrations were found to inhibit the skeletal formation of coral juveniles. Based on these data, we propose calcareous sediments in reef areas play a crucial role in mediating the impact of terrestrial runoff on corals by storing and releasing phosphate in seawater. We need more detailed surveys about phosphate bound to calcareous sediments near coasts for better managements of sustainable coral reef ecosystem services.