An experiment was performed on Britomart Reef (central region, Great Barrier Reef) to determine the effects of fish grazing and territoriality by the damselfish Hemiglyphidodon plagiometopon on benthic algal community structure. This pomacentrid excludes herbivorous fish from its territory, creating undergrazed patches with characteristic 'algal lawns' within coral reef lagoons. Pieces of natur...