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

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 degrees C at ambient. High levels of fertilization and normal ernbryogenesis were observed for Favites abdita. Favites chinensis and Mycedium elephantotus at temperatures to 32 degrees C (+5 degrees 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 degrees C (+4 degrees C), and fertilization ceased altogether at 34 degrees C (+6 degrees C). Early cell cleavage rates increased with temperature up to 32 degrees C for all species.