Hydrobiologia (2006) 565:39–58 Ó Springer 2006 R.S.E.W. Leuven, A.M.J. Ragas, A.J.M. Smits & G. van der Velde (eds), Living Rivers: Trends and Challenges in Science and Management DOI 10.1007/s10750-005-1904-8 Trophic relationships in the Rhine food web during invasion and after establishment of the Ponto-Caspian invader Dikerogammarus villosus M.C. van Riel1,4, G. van der Velde1,4,*, S. Rajagopal1,4, S. Marguillier2, F. Dehairs2 & A. bij de Vaate3,4 1Department of Animal Ecology and Ecophysiology, Section Aquatic Animal Ecology, Institute for Wetland and Water Research, Radboud University Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands 2Department of Analytical Chemistry, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium 3Ministry of Transport, Public Works and Water Management, Institute for Inland Water Management and Waste Water Treatment, P.O. Box 17, 8200 AA Lelystad, The Netherlands 4Member of Netherlands Centre for River Studies, P.O. Box 177, 2600 MH Delft, The Netherlands (*Author for correspondence: E-mail:
[email protected]) Key words: macroinvertebrates, invaders, ecotopes, food web, trophic relations, stable isotopes, Rhine Abstract The Rhine ecosystem is highly influenced by anthropogenic stresses from pollution, intensive shipping and increased connectivity with other large European rivers. Canalization of the Rhine resulted in a reduction of heterogeneity to two main biotopes: sandy streambeds and riverbanks consisting of groyne stones. Both biotopes are heavily subjected to biological invasions, affecting the rivers food web structure. The Ponto- Caspian amphipods, Chelicorophium curvispinum and Dikerogammarus villosus, have exerted the highest impact on this food web.