Molluscan hard-substrate associations in the Northern Red Sea

The mollusc associations of 29 hard-substrate localities in the Northern Bay of Safaga (Red Sea, Egypt) were studied. The hard substrates were classified into 7 types: reef flats, intertidal rock bottom, very shallow subtidal conglomerate, Porites carpel, faviid carpet, platy scleractinian association, Sarcophyton carpet. Based on a cluster analysis the molluscs of these hard substrates can be classified into 5 groups: Group A is dominated by Dendropoma maxima, Chamoidea and Tridacna maxima, group B by Pedum spondyloideum, T. maxima and Coralliophila neritoidea, group C by Chamoidea and Cerithium ruppelli, group D by Modiolus auriculatus, Chamoidea, Morula granulata and Nerita albicilla and group E by Chamoidea and Pitar hebraea. The latter group contains only samples which are generally poor in molluscs. Group A molluscs are diagnostic for reef flats, group B for Porites and faviid carpets, group C for Sarcophyton carpets and group D for tidal/shallow subtidal rock substrates. The different hard substrates are therefore characterized by diagnostic mollusc associations and some of them could also be identified in the fossil record.