Initial colonization, erosion and accretion of coral substrate

Blocks cut from Porites lutea were laid on the fore reef slope, reef flat and a lagoonal patch reef at Lizard Island, in the Northern Great Barrier Reef, and replicates removed from each environment at intervals of three months over a period of one and a half years. Variations in bioeroders and bioaccretors were noted. Microfaunas are far more numerous than macrofaunas as block colonizers; the principal borers are polychaete worms, whereas encrusters are molluscs, bryozoans, serpulids and solitary corals. The reef slope is more readily colonised by microfauna pioneer communities than are the other areas. All the environments exhibit a change from cirratulids to either sabellids or spionids (polydorids) over the length of the experiment. Accretion occurred on all blocks during the experiment, with significant differences detectable between environments; both reef slope and reef flat blocks showed weight increases of 9–10% whereas blocks from the patch reef showed increases of 15%. Annual erosion rates produced by polychaete worms are 0.694 kg m-2 year-1 (reef front), 0.843 kg m-2 year-1 (reef flat) and 1.788 kg m-2 year-1 (patch reef).