Spatial patterns of epilithic algal and detrital resources on a windward coral reef

Algae and detritus co-occur on reef substrata, but their relative importanc e to consumers, in terms of biomass and nutrient content, is poorly underst ood. Epilithic algae, sediment and detritus were sampled among four windwar d zones at Lizard Island, Australia, using a vacuum sampler. Total N, P and biomass (total organic C) were quantified for algae and detritus. Algal an d detrital biomass varied among zones and both were positively correlated w ith sediment load. Algal biomass was approximately six times higher than de tritus on the reef crest. In other zones, the two components were more simi lar in abundance. Particulates on the reef crest had the highest organic: i norganic ratios, a feature likely to be favoured by herbivorous and detriti vorous fishes. C:N ratios of algae and detritus, while locally variable, we re broadly comparable among zones. C:P ratios of both components decreased in leeward zones. Although locally variable, detritus had a higher content of both N and P. Overall, detritus is relatively abundant on windward reef substrata and of equal or greater nutritional quality than algae. It repres ents a potentially important resource for both detritivorous and herbivorou s fishes.