Coral recruitment: The critical role of early post-settlement survival

Coral recruitment is a pivotal factor in coral reef stability and in recovery following substantial disturbances. Despite its immense importance, the study of coral recruitment has some major gaps, notably larval survival before and following settlement, mainly due to technical limitations, which stem from the difficulty in observing the minute larvae. To overcome the major limitation in coral recruitment studies, i.e. the in situ detection of recruits during their early stages, we designed a new detection set-up, composed of a fluorescence detection set-up, a grid-covered substrate, and a Geographic Information System tracking system. This set-up, enabling the identification of coral recruits soon after settlement, revealed that in the critical period of the first day, less than 45% of the settling corals may survive. The results also suggest that either coral larva select locations that may increase their survival chances or they experience dramatic mortality during the early hours of settlement, which induce a consistent pattern of spat distribution. Our study confirms an earlier speculation that the first 24 h post-settlement may determine the rates and spatial patterns of recruitment. The significant implications of these findings, and the implemented "detection set-up" for coral reef monitoring and management, are discussed.