Factors affecting the distribution of the bivalve Donacilla cornea (Poli, 1795) in eastern Mediterranean sandy beaches MICHALIS MAVIDIS1*, ATHANASIOS KOUKOURAS1 and ANASTASIOS ELEFTHERIOU2 1 Department of Zoology, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece 2 Institute of Marine Biology of Crete, PO Box 2214, 710 03 Heraklion, Greece Abstract Donacilla cornea (Poli, 1795) is the characteristic bivalve of the midlittoral sand assemblage in the Mediterranean Sea. In order to acquire information on the factors influencing its distribution, a detailed survey was carried out on 117 sandy beaches in eastern Mediterranean. In each station, samples were taken from the lower midlittoral zone. Donacilla cornea was found in 56 beaches moderately exposed to wave action and with a mean particle size ranging from 325 to 1866 μm (medium to very coarse sand). This species was not found in sheltered or extremely exposed beaches. The abundance of this species was correlated with exposure to wave action, mean particle size and sorting index of the sediment. The percentage of CaCO3 and the organic matter in the sediment were not correlated either with the presence or the abundance of this species.   < back .