Recruitment failure of scleractinian corals in a subtropical marginal environment: Three-year monitoring in a Hong Kong marine park.

Coral recruitment was monitored for three years, using terracotta tiles, in two core coral areas in Tung Ping Chau Marine Park where coral coverage is one of the richest in Hong Kong. Results revealed an extremely low recruitment success of corals, with only 10 recruits recorded on 384 tile pairs, equivalent to 0.19 recruits myr throughout the study period. Recruits of Platygyra acuta pre-seeded on tiles that were subsequently grown in situ experienced very high mortality following settlement, with average mortality of 80% within half a month and <0.1% survival through the first four months of deployment. Data suggested that low recruitment of corals may be due to the lack of arrival of competent coral larvae, low larval settlement; and/or low post-settlement survival of recruits due to high sedimentation or intense competition for space with fouling organisms, e.g. algae, oysters, barnacles and bryozoans, which may negatively affect coral recruitment.