A comparative study of the mollusc communities of a Mediterranean saltwork (Marsala, Western Sicily.

Saltworks are peculiar artificial ecosystems and holds great interest for basic research. In fact the cooling vat (the first pond of the evaporating series) is a good example of a relatively closed area and can be considered an excellent in the field open-air laboratory, namely a mesocosm reproducing a simplified model of the natural condition of hyperaline lagoons. The aim of the present work was to analyse the structure, composition and distribution of molluscan assemblages and to identify the faunistic relationships between the cooling vat and the neighbouring basin of Stagnone di Marsala, beside considering exchanges between saltwork, Stagnone di Marsala and sea, on soft- bottom, covered by Cymodocea nodosa. In structural terms, two molluscan communities can be identified. As regard the saltwork, the community was always characterized by halolimnobic and euryaline species such as Ventrosia ventrosa, Loripes lacteus, Abra segmentum and Pirenella conica. while the community inhabiting Stagnone was composed mainly of marine taxa; here a good exchange with the sea is confirmed by the high values for species richness and diversity gives rise mainly to the presence of marine taxa: e. g Jujubinus striatus, Dikoleps nitens, Rissoa paradoxa, R. similis, Columbella rustica etc. The saltwork molluscan assemblage doesn’t seem to be similar to that of the Stagnone. The low specific richness, the high abundance and the low evenness, showed a pioneer stage of colonization, being poor in species and dominated by taxa with high abundance and low evenness