Succession, space and coral recruitment in a subtropical fouling community

Abstract

Patterns of recruitment and succession on ceramic settlement panels were examined in a subtidal marine community in eastern Australia to determine whether competition for settlement space with temperate biota was a factor potentially limiting the development of coral communities in a subtropical location. Replicate settlement panels were installed at Split Solitary Island (30˚S) in November 1992 and were destructively sampled after 1, 3, 5, 7, 10, 12, 16 and 29 months. Species richness and community structure data were analysed by non-parametric multivariate analysis. Space on panel surfaces was rapidly occupied; the upper surfaces by algae and the lower surfaces by bryozoans, ascidians and sponges, with a divergence of community structure over time. Of the 228 coral recruits identified on the panels, 98% were recorded on the upper surface of panels, in contrast to studies at most tropical sites where corals recruit predominantly to lower surfaces. Owing to the rapid settlement of other biota, free space for coral settlement was limited and this may account for the low coral recruitment rate recorded. High post-settlement mortality (>94%) of coral recruits over a 3-month period indicated the significance of post-settlement factors in accounting for low recruitment in settlement-panel studies.