Elucidation and modeling flow rate dependence on photosynthetic and calcification rates of hermatypic corals

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K12134
• 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: Tokyo Institute of Technology
• Principal Investigator: Nakamura Takashi 東京工業大学, 環境・社会理工学院, 准教授 (20513641)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: サンゴ / 光合成速度 / 石灰化速度 / 流速依存性 / 拡散境界層

Outline of Final Research Achievements

It is considered that coral metabolic rates are greatly affected by flow conditions. However quantitative assessment of this factor is completely lacking. In this study, the net photosynthetic and respiration rates of corals and the thickness of the diffuse boundary layer (DBL) were investigated using micro-dissolved oxygen electrodes under controlled flow velocity in a recirculating aquarium. In this result, it is confirmed that DBL thickness was proportional to the -0.8 power of the mean flow velocity. This is consistent with the theoretical and semi-empirical relationships of previous works. This leads to the conclusion that the rate of mass exchange at the coral surface is proportional to the 0.8th power of the mean flow velocity. However, photosynthetic and respiration rates did not correlate well with flow velocity, suggesting that they may be limited mainly not by material transfer at the coral surface but by other metabolic factors of corals.

Free Research Field

生態系モデリング

Academic Significance and Societal Importance of the Research Achievements

近年の大気二酸化炭素の増加に伴う地球温暖化や海洋酸性化は、海洋生物に様々な影響を与えることが予想され、その実態解明に向けた様々な研究が行われている。特に海洋酸性化はサンゴなどの石灰化生物の石灰化速度を低下させることが実験的に示されており、サンゴ礁生態系の衰退をもたらすことが危惧されている。一方で、流速の違いによる石灰化速度の変動幅は、海洋酸性化で予想されている成長速度の減少幅に比べて１桁大きい。本研究では、サンゴ表面での物質交換速度は流速の0.8乗に比例することが確認された。この流速依存性の感度は高く、本研究の成果は、サンゴ礁生態系の将来予測の精度を上げるためには非常に重要である。