SUBTROPICAL CORAL-REEF ASSOCIATED SEDIMENTARY FACIES CHARACTERIZED BYMOLLUSKS (NORTHERN BAY OF SAFAGA, RED-SEA, EGYPT)

The shallow marine subtropical Northern Bay of Safaga is composed of a complex pattern of sedimentary facies that are generally rich in moll uscs. Thirteen diver-taken bulk-samples from various sites (reef slope s, sand between coral patches, muddy sand, mud, sandy seagrass, muddy seagrass, mangrove channel) at water depths ranging from shallow subti dal to 40m were investigated with regard to their mollusc fauna > 1mm, which was separated into fragments and whole individuals. Fragments m ake up more than 88% of the total mollusc remains of the samples, and their proportions correspond to characteristics of the sedimentary fac ies. The whole individuals were differentiated into 622 taxa. The most common taxon, Rissoina cerithiiformis, represented more than 5% of th e total mollusc content in the samples. The main part of the fauna con sists of micromolluscs, including both small adults and juveniles. Bas ed on the results of cluster-, correspondence-, and factor analyses th e fauna was grouped into several associations, each characterizing a s edimentary facies: (1) ''Rhinoclavis sordidula - Corbula erythraeeasis - Pseudominolia nedyma association'' characterizes mud. (2) ''Microci rce sp. - Leptomyaria sp, association'' characterizes muddy sand. (3) ''Smaragdia spp. - Perrinia stellata - Anachis exilis - assemblage'' c haracterizes sandy seagrass. (4) ''Crenella striatissima - Rastafaria calypso - Cardites akabana - assemblage'' characterizes muddy seagrass . (5) ''Glycymeris spp. - Parvicardium sueziensis - Diala spp. - assem blage'' characterizes sand between coral patches. (6) ''Rissoina spp. - Triphoridae - Ostreoidea - assemblage'' characterizes reef slopes. ( 7) ''Potamides conicus - Siphonaria sp. 2 - assemblage'' characterizes the mangrove. The seagrass fauna is related to those of sand between coral patches and reef slopes with respect to gastropod assemblages, n umbers of taxa and diversity indices, and to the muddy sand fauna on t he basis of bivalve assemblages and feeding strategies of bi valves. T he mangrove assemblage is related to those of sand between coral patch es and the reef slope with respect to taxonomic composition and feedin g strategies of bivalves, but has a strong relationship to those of th e fine-grained sediments when considering diversity indices. Reef slop e assemblages are closely related to that of sand between coral patche s in all respects, except life habits of bivalves, which distinctly se parates the reef slope facies from all others.