BIVALVE DISTRIBUTION ON CORAL CARPETS IN THE NORTHERN BAY-OF-SAFAGA (RED-SEA, EGYPT) AND ITS RELATION TO ENVIRONMENTAL PARAMETERS

Bivalve assemblages on coral carpets in the Northern Bay of Safaga do not form distinct associations, but gradually shift in faunal composit ion. The taxonomic shift is accompanied by continuous variations in bi valve density and percentage of living individuals as well as by a cha nge of coral associations and potential bivalve habitats. The gradual lateral change of associations is best documented by Tridacna maxima a nd jewel box clams (Chamoidea) and is probably due to variations of th e suspension load in the water column. High suspension loads in the wa ter column are additionally indicated by 'giant oysters' (extremely la rge individuals of Hyotissa hyotis) and striking agglomerates of Lopha cristagalli. The vertical differentiation is best documented by the d ecrease of the zooxanthellate Tridacna maxima and is probably due to t he depth-dependent light penetration in the water column, which is att enuated in areas of high suspension load.