Influence of drainage from old mine deposits on benthic macroinvertebrate communities in central Swedish streams

We analysed the benthic macroinvertebrate species composition, taxonomic ri chness (as expected richness for 100 individuals), total abundance and biom ass at 117 stream sites in the province of Dalarna. Partial least squares r egression models were constructed from observations on undisturbed sites an d used to predict these community parameters at sites exposed to elevated l evels of copper, zinc, lead and cadmium resulting from leakage from old min e deposits. Species richness at undisturbed sites was positively related to the size of the catchment, pH, channel width. calcium concentration and th e proportion of deciduous trees in the riparian zone. In streams with eleva ted metal concentrations, we found reductions in taxonomic richness for tot al macroinvertebrates, mayflies, stoneflies and combined EPT (Ephemeroptera , Plecoptera and Trichoptera). but not fur that of Trichoptera nor total ab undance or biomass. Copper and zinc were those metals showing strongest neg ative associations with richness. Some ta,va, common at undisturbed sites, were missing at metal-polluted sites, These taxa were the mayflies Ameletus inopinatus, Ephemerella aurivilli and Heptagenia dalecarlica, the stonefly Protonemura meyeri and the caddisfly Apatania sp. (C) 1999 Elsevier Scienc e Ltd. All rights reserved.