Freshwater

bivalve invasions are nowadays a global phenomenon and some species, such as the zebra mussel, Dreissena polymorpha (Pallas, 1771), are listed amongst the most pervasive invaders in the world (Lowe et al., 2000). Bivalves are consi-dered key species in aquatic ecosystems, being capable of controlling and transforming their struc-ture and functioning through their filtering activity (Strayer et al., 1999). Thus, the establishment of alien bivalves often entails severe consequences at multiple levels in the newly occupied aquatic envi-ronments. These include dramatic changes in the diversity and abundance of benthic and planctonic communities, creation of new habitats, alterations in the rates of ecosystem processes or interference