Farming damselfishes shape algal turf sediment dynamics on coral reefs

Abstract

Farming damselfishes are well known for shaping benthic communities on reefs, in terms of both cultivating algae and increasing productivity. However, their capacity to shape relationships between algal turfs, detritus and sediments remains largely unknown, despite the importance of such relationships on reefs. We therefore examined the relationships between sediment loads and both algal turf length and detritus levels, inside and outside farming damselfish territories, at two reefs on the Great Barrier Reef. We found that, while sediment loads are tightly coupled with algal turfs outside territories, the nature of this coupling was fundamentally different inside damselfish territories, with significantly longer algal turfs and higher detritus levels prevailing, irrespective of sediment loads. These modified algal turf-sediment relationships may be a key factor in explaining, a) the significantly higher productivity levels reported from within farming damselfish territories and b) the ability of farming damselfishes to persist in high-sediment locations.

Keywords: Algal turf; Coral reef; Damselfish; Herbivory; Productivity; Sediment.