Abstract
Algal turf assemblages of the northern Great Barrier Reef, Australia, were sampled to determine the nutritional value of detritus and algae. Samples were collected with a suction apparatus across an exposure gradient from (1) the reef crest at highly exposed outer barrier reefs, (2) the reef crest of moderately exposed midshelf reefs, and (3) the reef slope of sheltered midshelf reefs. The biomass of algae and detritus decreased from sheltered midshelf reefs to moderately exposed midshelf reefs to highly exposed outer barrier reefs. This decrease was significant only for detritus (P −1 ) than in algae (11.8 ± 1.0 mg g −1 ). Starch content was significantly (P −1 ) than in detritus (6.0 ± 1.0 mg g −1 ). These results demonstrate that detritus is a potentially valuable food source to grazing fishes on coral reefs.