Effect of elevated temperature on fecundity and reproductive timing in the coral Acropora digitifera

The synchrony of spawning is of paramount importance to successful coral reproduction. The precise timing of spawning is thought to be controlled by a set of interacting environmental factors, including regional wind field patterns, timing of the sunset, and sea surface temperatures (SST). Climate change is resulting in increased SST, which is causing physiological stress in corals and could also be altering spawning synchrony and timing. In this study, we examined the effect of increasing seawater temperature by 2°C for 1 month prior to the predicted spawning time on reproduction in the coral Acropora digitifera. This short period of elevated temperature caused spawning to advance by 1 day. In animals incubated at elevated temperature, egg number per egg bundle did not change, however, egg volume significantly decreased as did sperm number. Our results indicate that temperature is acting both as a proximate cue to accelerate timing and as a stressor on gametogenesis to reduce fecundity. This finding suggests that increasing SSTs could play a dramatic role in altering reproductive timing and the success of corals in an era of climate change.