The aims of this study were to identify the taxonomic diversity and abundance of psammonic ciliate communities in mesotrophic and eutrophic lakes (Łęczna-Włodawa Lakeland, eastern Poland). The effect of selected physical and chemical water parameters on ciliates community was also analysed. Psammon samples were collected during three seasons: spring, summer and autumn of 2010. In each lake, in the psammolittoral, samples were collected in the euarenal, higroarenal, and hydroarenal zones. A total of 53 ciliate taxa were recorded. The highest value of the Shannon-Weaver index was recorded in summer in eutrophic lake (2.79). At the same time in mesotrophic lake, a lower value of the index was determined (0.79). The mean numbers of ciliates ranged from 516 ind.cm-3 in the eutrophic lake to 191 ind. cm-3 in the mesotrophic lake. In eutrophic lake, the highest number of ciliates was recorded in the euarenal (649 ind. cm-3), and the lowest in the higroarenal (425 ind. cm-3). In the mesotrophic lake, the highest average numbers were determined in the higroarenal (235 ind. cm-3), and the lowest in the hydroarenal (155 ind. cm-3). Irrespective of the lake trophy, Hymenostomata (Paramecium sp., Glaucoma sp., Uronema nigricans) occurred in the highest numbers (from 13 to 95%). The results demonstrated that N-NH4, P-PO4 and TOC can strongly regulate the abundance and taxonomic composition of ciliates. The strongest correlations between numbers of ciliates and physical and chemical water parameters were observed in the higro- and hydroarenal zones of the eutrophic lake.
The prevalence of heavy metals in wastewater is the cause of death of numerous organisms which take part in biological treatment of wastewater, that is why the aim of the study has been to asses the influence of cadmium and copper ions upon the microfauna of activated sludge. 5, 10, 50, and 100 mg/l of Cd2+ and Cu2+ were added into the samples of activated sludge and then, after 24 hours, the microscopic observations of activated sludge microfauna were carried out, and all changes concerning the amount of microfauna, functional groups, and species composition were determined. The results obtained allowed to find a high level of toxicity of Cd2+ and Cu2+ ions to activated sludge microfauna, which resulted in the changes in the value of the Sludge Biotic Index and classes of sludge, survivability of microfauna, and reduction in the number of taxonomic units. It was observed that Cu2+ ions are more toxic to activated sludge microfauna than Cd2+ ions in identical doses. Organisms sensitive to Cd2+ and Cu2+ ions have been found to be testate amoebae, Aspidisca sp. and Epistylis sp., as well as organisms relatively sensitive to tested metals, which turned out to be ciliates of Opercularia and Vorticella convalaria genera.