Recruitment of scleractinian corals in the Solitary Islands Marine Reserve, a high latitude coral-dominated community in Eastern Australia

Abstract

The Solitary Islands Marine Reserve (30 18' S, 153 30' E) is the site of the southern-most extensive coral communities on coastal eastern Australia. It has been hypothesised that lack of successful reproduction or recruitment of corals limits the distribution of corals at high latitudes. In this study, coral recruitment patterns were examined for 4 locations within the Solitary Islands Marine Reserve. Hard coral recruitment rate at the Solitary lslands (6.7 recruits per plate pair) was less than rates reported from similar studies at both the Great Barrier Reef (44 to 242 recruits per tile pair) and at Lord Howe Island (48.5 recruits per tile pair). Recruitment was spatially variable both within and between locations, and there was seasonal and inter-annual variability in recruitment success at 1 site. Recruitment of hard corals was dominated by planulating species, consistent with predictions made from coral recruitment patterns at Lord Howe Island, and in contrast with most previous studies of Pacific reefs. At the 2 most offshore islands, coral cover was dominated by Acropora sp., but the density of acroporid recruits was extremely low, suggesting that t h ~ s taxon may be reliant on sporadic recruitment from northern sites. In contrast with tropical sites where coral recruitment in shallow water is most frequent on downward fac~ng surfaces or crevices, corals settled abundantly on the upper-most surface of settlement plates at most sites. The difference in settlement orientation is possibly because of: (1) reduced light at high latitudes; (2) a reduction in herbivore abundance at high latitudes; (3) competition for settlement space on lower surfaces with abundant temperate species such as bryozoans and barnacles.