BIVALVE ASSEMBLAGES ON LIVING CORAL SPECIES IN THE NORTHERN RED SEA, EGYPT

Two sations northern Hurghada (Marine Biological Station and Ras El-Behar) were chosen during summer 2006 and winter 2007 to study and evaluate the compatibility of living bivalve assemblages on the living corals. Twenty-nine samples of hard corals contributed by living bivalves were collected using 0.25 m(2) aluminum square frame and were taken during daylight using SCUBA diving equipments. A total surveyed area of 132 m(2) and 534 bivalve individuals were counted from the studied sites and were associated with living corals, these individuals represented by 7 different families and 12 species. Pteriidae represented the highest individual numbers 229 (42.88%), whereae Veneridae recoreded the lowest number 11 (2.06%). Electroma alacorvi recored the highest presence 35.38% where as Gefrarium pectinatum had the lowest value 2.06%. There was a high association and correlationbetween density and standard deviation of the bivalves. Mytilidae and Pteriidae have a wide and strong association with some corals (as Stylophora pistillata; Porites solida; Pocillopora verrucosa; Favites abdita; Favites fluxuosa; and Goniastrea pictinata: Acropora pharonis; Montipora venosa; Acropora humilis, Anacropora spinosa and Montipora spingiosa). whereas Pectinidae, Arcidae, and Tridaenidae have a low coral association. Electroma alacorvi recorded the highest density 6.79 individuals 0.25 m(2) and a standard deviation +/- 2.41 whereas Barbatia setigera recorded the lowest density 1.9 individuals/0.25 m(2) (S.D +/- 0.78). Sedimentation rate and the large coral coverage play a major role in the bivalve assemblages, density and diversity where the highest coverage and dominance of Stylophora pistillata, Acropora spp., Porites solida, Favites spp., and Goniastrea pictinata were associated with high bivalve species density. Finally, the over-fishing activities, pollution particularly with oil and sedimentation are the major reasons for coral death causing absence of many bivalve species at Ras El-Behar.