REEF CORALS: AUTOTROPHS OR HETEROTROPHS?

¹ Discovery Bay Marine Laboratory, Department of Zoology, University of the West Indies, Mona, Kingston 7, Jamaica; and Department of Zoology, University of Edinburgh, Edinburgh, Scotland

The assumption that reef corals are wholly autotrophic due to the presence of zooxanthellae is questioned. Reef corals lack the behavioral and structural specializations for an autotrophic existence comparable to that found in the xeniid octocorals and zoanthideans which appear to depend upon zooxanthellae for their food.

The heterotrophic nutritional activities of reef corals, as observed both in the field and in the laboratory, include the following: (1) specialized carnivorous feeding, primarily on zooplankton, facilitated by ciliated currents and mucus, direct transfer of prey to the mouth by the tentacles, or extracoelenteric feeding by the mesenterial filaments; (2) unspecialized detritus feeding, involving the use of a wide range of organic matter of animal and perhaps of bacterial origin; (3) direct utilization of dissolved or colloidal organic matter as suggested by the uptake of amino acids by the epidermis and by the ultrastructural, histochemical and physiological features of the free cell border.

Water circulating within the reef, the boundary layer water, is in a continuous and dynamic exchange with the trophic structure of the reef, recycling nutrients with the benthos and making the suspended particulate matter a possible food source for corals.

This article has been cited by other articles:

				C. R. WILKINSON Net Primary Productivity in Coral Reef Sponges Science, January 28, 1983; 219(4583): 410 - 412. [Abstract] [PDF]