LATITUDINAL VARIATION IN PATTERNS OF COLONIZATION OF CRYPTIC CALCAREOUS MARINE ORGANISMS

Few studies of fouling communities have directly compared colonisation patterns over wide geographical scales in similar community types. In this study, the recruitment and early growth of calcareous cryptic fo uling organisms were examined on settlement panels at 2 tropical and 2 subtropical locations at varying distances from the mainland in easte rn Australia. Species diversity and cover on the settlement panels aft er 6 mo were higher at the subtropical inshore site than at any of the offshore or tropical sites. Classification of the sites by multivaria te cluster analysis and ordination showed clear distinctions between i nshore and offshore sites, while sites separated by approximately 14 d egrees of latitude were less clearly distinguished. Inshore/offshore v ariation in the physical environment, especially turbidity and eutroph ication, and the effects of longshore currents in the regions are poss ible explanations for these patterns. There was a significantly higher weight of calcified material at the subtropical inshore site than at the other 3 sites, attributable to higher cover of both bryozoans and barnacles; these taxa are likely to make a significant contribution to community calcification rates in subtropical coral communities. Compe tition for space with encrusting species is proposed as a potential me chanism limiting coral recruitment in coastal subtropical eastern Aust ralia.