Effects of Benthic Algae on Sessile Animals: Observational Evidence from Coral Reef Habitats

Opportunist sessile animals are probably less abundant in well-lit than in dark places on a coral reef as a result of the presence of algae. The effects of the algae on sessile animal species were investigated using observations from settlement panels exposed in the same way for the same period at sites inside and outside caves. These observations suggest that filamentous algae interfere with the feeding structures of arborescent bryozoans, and that bryozoan vibracula may function to reduce this effect. In addition, in places exposed to fish, the presence of algae around sessile animals apparently renders them liable to damage by scraping herbivorous fish, so that the herbivores effectively “weed out” sessile animals from algal lawns.