Effects of particulate peat on the behavior and physiology of the Jamaican reef-building coral Montastrea annularis

Corals in an in situ respirometer exposed to suspended peat during the day greatly decreased net oxygen production, probably due to a reduction of intensity and spectral quality of light reaching the symbiotic zooxanthellae. Net production returned to pre-exposure levels after the chambers were cleared; the corals showed no behavioral effects. In contrast, after exposure during the night, corals displayed clearing behavior (such as extreme distension of the coenosarc and trapping of peat particles in thick clumps of mucus) and an increase in respiration rate comparable to the decrease in net production observed during the daytime exposure. The following morning, net production values were significantly lower than pre-exposure production values although ambient light intensity was slightly higher. This decrease in production as well as a 22% reduction of chlorophyll content in the coral tissue indicated loss of zooxanthellae from the stressed corals. Long-term exposure to such a stress could reduce coral growth rates and substantially alter coral reef communities.