CORAL REEF RECOVERY FOLLOWING EXTENSIVE DAMAGE BY THE "CROWN-OF-THORNS" STARFISH, ACANTHASTER PLANCI (L.)

Abstract

A recent infestation of the "Crown-of-Thorns" starfish, Acanthaster planci (L.), killed a high proportion of the fringing reefs of Guam. This study is a distributional analysis of the state of the extant coral community to determine whether or not recovery is taking place. The study region is located at Tanguisson Point, Guam, where prior to the starfish predation a well developed fringing reef occurred. This region was heavily infested by an Acanthaster planci population from June, 1968 to September, 1968. The infestation resulted in the death of more than 95 percent of the reef building (hermatypic) corals. Distributional analysis of the reef corals was undertaken in 1970 with the establishment of three permanent transects in the study area. The distributional analysis includes: 1) species diversity and the relative abundance of each species; 2) percentage of substratum surface occupied by living corals for each reef zone; 3) distribution of corallum size by reef zone; and 4) distribution of coral growth forms by reef zones. In 1971, one year later, a second distributional analysis of reef corals was conducted on the same transects. A comparison of data from the two periods indicates that some reef recovery is taking place, and changes have occurred in all the above parameters studied. Species diversity has increased in all reef zones. A total of 33 genera and 96 species were recorded in 1970. One year later 38 genera and 111 species were found. Percentage of substratum covered by living corals has increased in all reef zones except the reef margin. Increases in percentage of living coral cover range from 1.6 percent on the seaward slope zone to 3 percent on the submarine terrace and reef front zones. The total number of coral colonies recorded on the transects has increased from 1302 in 1970 to 2116 in 1972. This increase in the number of newly established coral colonies has resulted in a net decrease in average corallum size. There has been an increase in the number of colonies with incrusting growth forms and a decrease in colonies with massive growth forms.