Experimental analysis of recruitment in a scleractinian coral at high latitude

A set of field experiments were conducted to determine the patterns of dispersal and recruitment in the brooding scleractinian coral Pocillopora damicornis at high-latitude (32°N), temperate locations in Amakusa, south-western Japan. Planulation occurred only in July (from full moon to last-quarter moon) in 2 consecutive years, confirming a pattern of annual reproduction in this species at the study site. Settlement plates placed beside naturally occurring colonies of P. damicornis accumulated more recruits than plates placed away (8 m) from the colonies in both years. Another experiment involving transplantation of P. damicornis colonies into an area where the species did not naturally occur but where environmental conditions were considered adequate for its growth also demonstrated that the density of settling planulae was high close to parent colonies but declined steadily with increasing distance. Planulae distribution tended to be more aggregated with increasing distance from their source. The present study demonstrates that the planulae of brooding coral species do not generally disperse over long distances at high latitude.