Decreasing salinity and initial reactions of the macrozoobenthos in the rivers Werra and Weser
Correlated with recent reductions in the salinity of the Werra and Weser, the benthic community of the river system has changed. Since 1993 the upstream region of the Weser is now dominated by four species of Hydropsyche (Trichoptera). Three species of Corophium (Amphipoda) occur throughout the Mittelweser in different areas according to the salinity-gradients. The benthic biocoenosis is dominated by filter-feeders, and other functional components of the foodweb are only rudimentarily developed.