Fine sedimentation affects CPOM availability and shredder abundance in Alpine streams

Fine sedimentation was quantified in the upper stretch of the Pellice river basin (Italian Alps), in an area partially disturbed by mining activities. Sediment traps were placed in 52 sites and benthic samples were collected to assess the amount of coarse particulate organic matter and the structure of macroinvertebrate community. The results indicated that the increase of fine sediment in the river reduced the amount of coarse particulate organic matter, affecting the abundance of invertebrate shredders. In small alpine streams, where allochthonous organic matter is the main energy source, fine sedimentation reduces the availability of trophic resources, affecting the abundance of benthic communities.