Digging the mud: Attempts to abate siltation in pearl mussel rivers
2 Schmidt & Partner GbR
O 2.1 in Biodiversität, Arten- und Naturschutz
15.04.2010, 13:00-13:15, H13
Directly at the former ‘Iron Curtain', in the tri-border region of Bavaria - Saxony - Czech Republic, many threatened species and plants, among them the river pearl mussel Margaritifera margaritifera and the common river mussel Unio crassus have been preserved in a number of streams. In the course of the 20th century the number of pearl mussels decreased significantly. Besides contamination from pollutants and nutrients, particularly the siltation of the bottoms of the streams resulted in missing offspring of mussels, since young mussels suffocate in the clogged gravel. In several projects a variety of actions have been implemented at different streams to reduce the mud drag-in. Monitoring results and examinations were used to critically evaluate the implemented measures and concepts: Mud collectors, though removing significant amounts of mud, are not sufficiently effective with respect to fine sediment fractions. The improvement of cleaned gravel was sustained for several years. However, the cleaned sediment was not stable, which is prerequisite for young mussel habitats. We argue that local measures in and near the river may contribute to habitat restoration, but the problem of siltation has to be addressed by preventing soil erosion and transport of fine sediments in the whole river catchment. Troubles and possibilities of the abatement of siltation in the agricultural landscape are discussed.
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