Thermal tolerance of the hermatypic coral Acropora tenuis elucidated by RGB analysis and expression of heat shock proteins in coral and symbiotic dinoflagellates

Shitaoka, Rin; Ishibashi, Hiroshi; Takeuchi, Ichirō

Thermal tolerance of the hermatypic coral Acropora tenuis elucidated by RGB analysis and expression of heat shock proteins in coral and symbiotic dinoflagellates

2021

Shitaoka, Rin | Ishibashi, Hiroshi | Takeuchi, Ichirō

Increased seawater temperature has resulted in mass coral bleaching events globally. Acropora tenuis, the dominant hermatypic coral species in southern Japan, was exposed to four temperature treatments [28 °C, 30 °C, 32 °C, and >32 (=33.3 °C)] for 7 d. The coral colour was converted to R (red), G (green), and B (blue) values, each ranging from 0 (darkest) to 255 (brightest). RGB values exposed to 28 °C and 30 °C decreased slightly, whereas those exposed to 32 °C increased significantly after day 3–6, and those exposed to 33.3 °C changed to white within 2 d. Quantitative RT-PCR analysis revealed no significant changes in heat shock proteins in Acropora and symbiotic dinoflagellates at 28 °C and 30 °C after a 7 d exposure. Our findings revealed that 30 °C, higher than the mean temperature of the warmest month in southern Japan, was an inhabitable temperature for A. tenuis.

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