Torgny Wiederholm

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The occurrence of deformed mouth parts in recent and subfossil material of mostly Chironomus, Micropsectra and Tanytarsus increased from less than 1 % of the larvae at unpolluted sites or time periods to figures in the range of approx. 5–25% at strongly polluted sites. Deformities occurred in species that are widely separate in taxonomic position and way of(More)
Three major lake clusters, corresponding to different trophic categories of lakes, were identified in a group average cluster analysis of 34 lakes and 33 profundal chironomid taxa. The classification of chironomids was not as distinct as that of lakes, presumably because of the incomplete identification of species. Groups of chironomid taxa associated with(More)
The amphipod Monoporeia a&is (LindstrGm) exhibits long-term population oscillations in oligotrophic Lake V&tern. Correlation showed profundal oxygen and temperature, and intraspecific and predatory interactions to be poor explanatory variables. Conversely, the interannual variability in food availability-diatom biovolumewas highly correlated with amphipod(More)
Changes in the composition of chironomid remains from three 65–76 cm deep cores of profundal sediments reflect changes in the lake's trophic state during a period of approximately 150 years. A long period of moderate eutrophication and successively increasing chironomid numbers was followed by a rapid change in productivity resulting in the disappearance of(More)
Sediments from four lakes polluted by effuents from steel industries and from two reference lakes were investigated. The sediments contained elevated concentrations of oil, Pb, Cd, Hg, Zn, Ni and Cr in different combinations. The toxicity of the polluted sediments to Daphnia was much higher than reported elsewhere (24-h LC50 0.5–1.5 vol%). Tubifex survived(More)
Pontoporeia affinis Lindström predominated profundal macroinvertebrate communities in eutrophic Lake Mälaren. Amphipod densities, at both stations studied, averaged > 50% of overall total macroinvertebrate densities. The life history of P. affinis was two years, with two cohorts distinguished, both exhibiting similar patterns in annual growth. During the(More)
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