Effects of coral extracts on survivorship, swimming behavior, and settlement of Pocillopora damicornis larvae

Abstract

Coral larvae released into the water column encounter different dissolved chemical cues secreted by organisms on the substratum that are engaged in spatial competition. These cues initiate vital biological processes in the larvae. In this study, the effects of crude extracts from the scleractinian corals Pocillopora damicornis and Porites cylindrica, and the soft coral Sarcophyton glaucum, on the survivorship, swimming behavior, and settlement of Pocillopora damicornis larvae were evaluated. High concentrations of heterospecific coral extracts caused a significant decline in both larval survivorship and settlement whereas conspecific extracts did not result in any larval mortality. Exposure to heterospecific extracts resulted in repulsion of larvae as indicated by a transient change in larval morphology and sustained swimming in the upper water column. In contrast, the conspecific extract enhanced larval exploration of both the water column and substratum and was able to induce larval settlement. These results suggest that chemical cues emanating from conspecifics and other coral species are capable of altering the biology of coral larvae, thus potentially influencing settlement behavior and species distribution on the reef.