Ingestion and transformation of algal turf by Echinometra mathaei on Tiahura fringing reef (French Polynesia)

The sea urchin Echinometra mathaei is the most abundant herbivore on many t ropical reefs. We studied the ingestion and digestion diel rhythms, transfo rmation of algal turf and bioerosion attributable to this species on the Ti ahura fringing reef in French Polynesia. Ingestion rates showed a circadian rhythm with most feeding tailing place during the night. Absorption of foo d occurred throughout the day with urchins digesting food outside of the fe eding period. A total of 73% of the faecal pellets consisted of CaCO3 erode d from the reef, 20% consisted of organic matter and 7% the refractory orga nic matter. Of the organic matter, lipids, carbohydrates and chlorophyll we re digested and absorbed and proteins were expelled in the faecal pallets. An average individual bioerosion of 0.32 g day(-1) was estimated for E. mat haei from approximately a 35-mm test diameter on thc Tiahura fringing reef. We further estimated that E. mathaei release 70.5 g m(2) y(-1) of carbohyd rates. 43.8 g m(2) y(-1) of lipid, 23.3 E m(2) y(-1) of protein and 2.0 g m (2) y(-1) of total chlorophyll pigments. (C) 2000 Elsevier Science B.V. All rights reserved.