Settlement, Mortality and Recruitment of a Red Sea Scleractinian Coral Population

Abstract

Connell (1974 reviewed different aspects concerning the distribution and abundance of hermatypic corals and pointed out the many gaps in our knowledge of the population ecology of corals. Thus, very little is known on the capacity of larval dispersal, survivorship, and conditions for settlement of hermatypic corals. These areas of ignorance are among the main obstacles to an understanding of life histories of these organisms (Grassle, 1974. Although the settlement behavior and population dynamics of coral planulae have not been studied in the field, the rate of settlement and early survival have been followed in two cases (Stephenson and Stephenson, 1933; Connell, 1974). Stephenson and Stephenson (1933) placed on the reef at Low Isles different artificial objects as settling surfaces for coral planulae. They used logs of wood, pieces of beach- sandstone, earthenware drain pipes, glass jars, and cleaned shells of clams. About 40 young colonies settled on these materials during a period of 11 months. Of 36 colonies recovered, 26 were Pocillopora bulbosa, which might indicate the opportunistic character and colonizing capacity of this species. Connell (1974) marked permanent quadrats on the reef flat at Heron Island, Great Barrier Reef and took photographs at intervals since 1962, for 12 years. He found that the average rate of recruitment for all species between 1962 and 1970 was about 5 new colonies per square meter annually. In all areas the commoner species had high rates of recruitment and mortality and maintained their abundance.