Large-scale patterns in internal bioerosion of Porites: cross continental shelf trends on the Great Barrier Reef

Abstract

Internal bioerosion of the coral Porites lobata (Coelenterata, Scleractinia) was examined on 5 reefs across the central region of the Great Barrier Reef, Australia: Orpheus Island, Britomart Reef, Rib Reef, Davies Reef, and Myrmidon Reef. Ninety corals were sliced into discs (n sub(t) = 270 replicates) and X-rayed to identify internal bioeroders and quantify the degree of bioerosion caused by each bioeroding group. Total internal bioerosion decreased significantly with distance offshore, across the continental shelf. Abundances of bivalves and sponges decreased the most significantly. Sponges were significantly lower on the outer shelf. Abundance of sipunculans and polychaetes showed only a nominal decrease across the shelf. Boring bivalves dominated the inshore area while the relative (polychaetes and sipunculans) remained generally constant across the shelf.