Damage and recovery of four Philippine corals from short-term sediment burial

Recovery of corals after full burial with littoral sediment (16 % silt, 46 % fine sand and 38 % coarse sand; 28 % CaCO3) was monitored in 2 field expe riments at the reefs off Lucero, Bolinao (Pangasinan, NW Philippines), from April to May 1996. In the first experiment at 2 m depth. Porites was burie d for 0, 6, 20 and 68 h; a second experiment was done at 5 m depth and 4 co mmon taxa (Porites, Galaxea, Heliopora and Acropora) were buried for 20 h. At 2 m depth, Porites was not affected by 6 h burial compared to the contro ls that were not buried. Increasing burial time had increasingly more serio us effects. Burial for 20 h resulted in increased discoloration of the cora l tissue. After 68 h of burial, up to 90 % of the tissue bleached in the fi rst days. About 50 % of this tissue disappeared subsequently and bare coral skeleton became exposed or were covered with algae. After a few weeks, how ever, recovery took place: the bare areas were recolonized from surrounding surviving tissue or from highly retracted polyps in the affected area. In the corals that had been buried for 20 h no more significant differences fr om the controls were observed after 3 wk. For those that were buried for 68 h, this was the case after 4 wk. At 5 m depth, all Acropora died after the 20 h burial treatment, but the other taxa recovered in a comparable way to the Porites in the first experiment at 2 m depth. It is concluded that com plete burial will cause considerable whole-colony mortality in at least Acr opora, and thus may result in a permanent loss of coral taxa from reefs tha t are subject to such intense sedimentation events. Less sensitive taxa inc ur substantial damage but significant recovery was observed after a month.