Structuring effects of chemicals from the sea fanPhyllogorgia dilatataon benthic communities

Abstract

Despite advances in understanding the ecological functions of secondary metabolites from marine organisms, there has been little focus on the influence of chemically-defended species at the community level. Several compounds have been isolated from the gorgonian octocoralPhyllogorgia dilatata, a conspicuous species that forms dense canopies on rocky reefs of northern Rio de Janeiro State, Brazil. Manipulative experiments were performed to study: (1) the effects of live colonies ofP. dilatata(physical presence and chemistry) on recruitment of sympatric benthic organisms; (2) the allelopathic effects of its chemicals on competitors; and (3) chemotactic responses of the non-indigenous brittle star,Ophiothela mirabilis. Early establishment of benthic species was influenced on substrates around liveP. dilatatacolonies and some effects could be attributed to the gorgonian’s secondary metabolites.In addition, the gorgonian chemicals also exerted an allelopathic effect on the sympatric zoanthidPalythoa caribaeorum,and positive chemotaxis uponO. mirabilis. These results indicate multiple ecological roles of a chemically-defended gorgonian on settlement, sympatric competitors, and non-indigenous species.