Taxonomic diversity and structure of the molluscan fauna in Oualidia lagoon (Moroccan Atlantic coast).

The spatial distribution of the molluscan fauna of Oualidia lagoon (Moroccan Atlantic coast) was studied during winter 2013. Samples were collected from 43 stations over the whole of the lagoon. Twenty-eight taxa (19 species of gastropods, 7 species of bivalves, 1 species of polyplacophora, and 1 species of cephalopod) were listed, 21 of which are newly reported for Oualidia lagoon. Four taxa, Hydrobia sp. (78.29%), followed by Abra alba (13.99 ), Nassarius pfeifferi (5.07%), and Cerastoderma edule (1.32%), were accounted for 98% of the total abundance. A classification analysis used to characterize the lagoon on the basis of molluscs showed the existence of three main clusters from downstream to upstream: a Nassarius pfeifferi community, a Hydrobia sp.-Abra alba community and a Hydrobia sp.-Cerastoderma edule community.