Sediment rejection by reef corals: The roles of behavior and morphology in Montastrea cavernosa (Linnaeus)

The sediment rejection abilities of colonies of Montastrea cavernosa (Linnaeus) were monitored in a series of field and laboratory experiments. Under conditions of natural sediment deposition, colonies were capable of removing virtually all sediment from their surfaces. Equivalent sections of dead coral skeleton accumulated as much as 345 mg sediment · 25 cm^-2 · day^-1. Laboratory experiments show the sediment rejection process to consist of passive and active phases. Passive movement of sediment off colonies occurs at the time of initial sediment impact. Fine grain size, tall polyps, and convex colonies all enhance passive removal. Active removal involves the behavioral responses of the colony and is independent of sediment type or colony morphology. The presence of appropriate morphologies can increase the proportion of sediment passively removed and reduce the amount of work a colony must perform to keep its surface clear of sediment.