Differing effects of thermal stress on coral fertilization and early embryogenesis in four Indo Pacific species

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Coral reefs are expected to be severely impacted by rising seawater temperatures associated with climate change. The fertilization and early embryogenesis of four reef-building coral species representing three Indo-Pacific families were examined in a series of laboratory experiments where temperatures were increased up to 5–6°C at ambient. High levels of fertilization and normal embryogenesis were observed for Favites abdita, Favites chinensis and Mycedium elephantotus at temperatures to 32°C (+5°C) and embryos developed normally until the 5th cell cleavage. Acropora millepora was the only species to be affected by higher temperatures, exhibiting significantly reduced fertilization and a higher frequency of embryonic abnormalities at 32°C (+4°C), and fertilization ceased altogether at 34°C (+6°C). Early cell cleavage rates increased with temperature up to 32°C for all species.