Preliminary observations about the coexistence of Dreissena polymorpha, Corophium curvispinum and Corbicula spp. in the River Moselle.

Benthic macroinvertebrates were sampled at a water depth of 1-4 metres by means of benthic dredges along several transects of the River Moselle from July 1994 to September 1995. These samples revealed the recent establishment of the amphipod Corophium curvispinum and of two forms (or species?) of the genus Corbicula (Bivalvia). Our sampling programme showed that the biogeographical distribution of C. curvispinum included the French part of the River Moselle at least up to Gondreville (i.e. 137.5 km newly colonized), and that Corbicula spp. colonized the River Moselle up to Dieulouard (i.e. 337 km from the confluence of the river with the Rhine). The distribution of these species, considered as mass invaders that may cause serious fouling problems for river water users, seems to be correlated with characteristics of the substratum. Spatial and trophic competition between these new immigrants and previously established macrobenthic populations are possible. The structure and the dynamics of these populations must now be carefully observed, in order to prevent possible economic and ecosystemic damages.