Effects of water cycle and phosphorus load on coral calcification mechanisms in subtropical islands

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K12310
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 63010:Environmental dynamic analysis-related
• Research Institution: University of the Ryukyus
• Principal Investigator: Yasumoto Jun 琉球大学, 農学部, 助教 (70432870)
• Co-Investigator(Kenkyū-buntansha): 安元 剛 北里大学, 海洋生命科学部, 講師 (00448200)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 島嶼特有の水循環 / リン酸塩負荷 / サンゴの石灰化機構 / 蓄積リン

Outline of Final Research Achievements

The objectives of this research are to estimate the acceptable daily phosphorus load (LD) for coral growth based on the correspondence between the total daily phosphate load (TDPL) and accumulated phosphorus in sea sediments. TDPL was estimated in conjunction with the results of field observations and integrated three-dimensional water cycle model.
Based on the relationship between accumulated phosphorus and the number of juvenile corals in the study site, the threshold value of accumulated phosphorus was estimated to be 3.0 uM. A high positive correlation was observed between accumulated phosphorus and the total daily phosphorus load in the study site. The acceptable total daily phosphorus load for coral growth was estimated to be about 100 g-P/m3/day. These results confirm our hypothesis that terrestrial-derived phosphate is transported to the ocean through the water cycle and adsorbed on calcareous sediments, inhibiting coral growth.

Free Research Field

地下水文学

Academic Significance and Societal Importance of the Research Achievements

これまで過度の栄養塩が海に流れ込むと，その海域のサンゴが減少することは知られていたが，科学的なメカニズムはわかっておらず，具体的な対策も取られていなかった。本研究の成果は，世界規模で減少するサンゴ礁の保全に大きく貢献できると期待できる。また，CO2の固定化技術の開発は国内外での重要な課題と位置付けられており，サンゴの石灰化を模したCO2固定化技術の開発に繋げる予定である。