Widespread but variable toxicity in scleractinian corals.

Aqueous and/or aqueous ethanol extracts were made of 58 scleractinian species from 11 families, collected from Heron Island, Great Barrier Reef. At least one extract from each of 53 species (91%) exhibited activity against at least one bioassay system. Extracts from at least one colony of each of 41 species of the 58 tested were toxic to mice when injected i.p. Cytolysis of sheep red blood cells was produced by extracts from at least one colony of each of 49 species of the 57 species tested and antibacterial activity was present in extracts from at least one colony of each of 37 species of the 55 tested. Only four species from 45 species assayed yielded extracts toxic to mosquito fish. This is the first report of bioactivity in extracts of 46 species of coral and the first report of bioactivity of extracts of corals from the families Mussidae, Merulinidae, Siderastreidae, Oculinidae and Dendrophylliidae. Variable results on a particular bioassay exhibited by extracts from different colonies of a given species were analysed by the Generalized Linear Interactive Modelling system (GLIM). Toxicity to mice, cytolytic and antimicrobial activity are not significantly correlated with each other. No model could be generated to explain the variation in the incidence of cytolytic activity nor of antimicrobial activity. However antimicrobial activity varied significantly between collection trips and was negatively associated with the presence of immature gonads in the colonies. The model predicts that toxicity to mice will be higher in extracts collected when average maximum monthly air temperature is high.