In situ release of mucus and DOC-lipid from the corals Acropora variabilis and Stylophora pistillata in different light regimes

Rates of mucus and DOC-lipid release were determined for colonies of Acropora variabilis and Stylophora pistillata at 5 m depth and for a colony of A. variabilis at 23 m depth. In addition, colonies at 5 m were shaded to simulate ambient irradiance at 6 m, 10 m and 16 m depth to evaluate the effect of light on the rates of release. A. variabilis released more mucus and DOC-lipid at 5 m than at 23 m depth. For both corals, the night rates were about 30% those of the day. A reduction in total integrated irradiance decreased mucus output from the corals. Similarly, DOC-lipid release showed a diurnal pattern and diminished with reduction in daily irradiance. For both coral species, DOC-lipid release rates were greater in the afternoon than in the morning. The night rates were less than 55% those of the day. The DOC-lipid comprised wax esters and a phospholipid fraction. The diurnal variation was due to changes in yield of wax esters which contributed >90% of the carbon released as DOC-lipid. In situ release of mucus and DOC-lipid was infuenced by light effects on phototrophic carbon metabolism. A daily budget for carbon released as mucus and DOC-lipid was estimated for each coral species at 5 m depth.