Our field experiments demonstrate that vermetids can have deleterious effects on four species of coral. Ambient densities of D. maximum reduced coral growth by up to 82 per cent and survival by up to 52 per cent. Experimental results were concordant with field surveys, in which vermetid densities were positively correlated with dead coral for P. lobata, P. rus and Pocillopora, but not Montipora. Two other studies (one experiment in Guam: Colgan 1985; and one observational study in the Red Sea: Zvuloni et al. 2008) suggest the negative effects of vermetids on corals, which we observed in Moorea may also occur in other locations. Our research strengthens and extends the inferences drawn from these previous two studies (one based upon correlative evidence, the other published in symposium proceedings; both focused on a single coral species). Importantly, our field experiments demonstrate interspecific variation in the responses of corals to D. maximum, which collectively suggest that vermetids may alter the structure of coral communities (e.g. electronic supplementary material, appendix C).
