How do corals determine the hour of spawning?

Corals have a remarkable ability to synchronize their spawning activities, and this synchronization is largely dictated by environmental cues, particularly the timing of sunset. Corals typically spawn at night, and they often do so around the time of a specific lunar phase, which can also be influenced by the timing of sunset. As the sun sets, the dimming light can trigger biological processes within the coral, prompting them to release their gametes into the water.

This reliance on sunset as a cue allows corals to maximize reproductive success by ensuring that their larvae are released when conditions are suitable for dispersal and avoiding predation. The other options may involve external environmental factors influencing marine life, but they do not precisely dictate the timing of coral spawning as effectively as sunset does.