MASSIVE CORALS ARE REGULARLY SPACED - PATTERN IN A COMPLEX ASSEMBLAGEOF CORALS

In November 1994, 955 colonies of scleractinian coral occupied approxi mately 17% of a 15 x 7 m study area which formed part of an intertidal platform near the reef crest at Heron Island Reef off the NE Australi an coast. Of these colonies 468 (49%) were massive corals and 487 (51% ) were nonmassives. When 50 colonies belonging to unidentified species of Porites were excluded there remained 418 massive corals belonging to 28 species and 12 genera. Twenty of these species were represented by fewer than the mean number of 13 colonies and 44% of all colonies o f the massive corals present belonged to the species Favites abdita, M ontastrea curta and Montastrea annuligera. Although the colonies of ma ssive corals rarely exceeded 50 cm in diameter, they fell into a wide range of sizes. However, the majority of colonies of most species had diameters >10 cm. Mean annual growth rates varied among species and am ong colonies of the same species but for most colonies was less than o r equal to 0.5 cm in diameter yr(-1). The total number of colonies of massive corals (excluding colonies of the genus Porites) increased fro m 382 to 418 from November 1991 to November 1994, with settlement slig htly in excess of mortality each year. However, the total area occupie d by massive corals remained essentially constant during this period. Most species of massive corals showed no mortality and the low mortali ty exhibited by each of the remaining species was compensated for by s ettlement of new colonies. The massive coral colonies were regularly s paced, with a mean centre to centre spacing distance of 27.5 +/- 15 cm (SD), a mode of 17 cm and a median of 24 cm. Nearest neighbours were rarely of the same species. We propose that the establishment and main tenance of a structural matrix of massive coral colonies exhibiting th e regularly spaced pattern described are based on the release of allel ochemicals from these colonies.