The Dese estuary (lagoon of Venice, Italy): a case of study for biodiversity at the community level.

Distribution of mollusc and polychaete communities in the Dese estuary were analysed in spring, Summer and autumn. The benthic communities follow a distribution pattern which is affected by salinity gradient and established through different assemblages of species. This pattern, evident in spring, is modified from summer to autumn because of the explosion of Streblospio shrubsolii. Possible Explanations include not only the role played by temperature and trophic conditions as factors Determining the increase of S. shrubsolii populations but also competition due to different degrees of opportunism of dominant species.