Dratów, Krzczeń and Tomaszne lakes are among environmentally valuable reservoirs in Poland and Łęczyńsko-Włodawskie Lakeland. These are shallow eutrophic reservoirs of varied water surface. What they have in common is the fact that they are linked by Wieprz-Krzna Canal. The main aim of the present study was to determine the degree of faunistic similarity between planktonic rorifer assemblages inhabiting these particular lakes. The authors were interested to find out whether linking the lakes with the canal, as well as currently applied water exchange could affect the degree of faunistic similarity occurring between these lakes. Physical and chemi-cal analyses, as well as the studies of planktonic rotifers were carried out in the spring, summer and autumn of 2012 and 2013. They included determining the qualitative composition and the density of planktonic rotifers. The studies resulted in finding 50 species of Rotifera, with mean density ranging from 75 to 855 ind. dm-3. The dominants included the common species of Keratel-la cochlearis, Keratella cochlearis tecta, Keratella quadrata, Polyarthra vulgaris, Kellicottia longispina, Brachionus angularis, Ascomorpha odalis and Synchaeta pectinata. The results re-vealed high faunistic similarity among rotifer assemblages inhabiting a particular lake in different years, and high diversification occurring between the lakes compared in the work. The analyses showed that linking the lakes by Wieprz-Krzna Canal did not significantly affect the faunistic similarity of these particular lakes.
Dratów, Krzczeń and Tomaszne lakes are linked by means of Wieprz-Krzna Canal. On the other hand, Bikcze, Mytycze and Plotycze lakes are not included in the water system of Wieprz-Krzna Canal. However, all these lakes are regarded as biologically valuable water reser-voirs forming Łęczyńsko-Włodawskie Lakeland. They are shallow eutrophic lakes with varied water surface, different catchment area and diversified structure of catchment management. The qualitative and quantitative composition of planktonic rotifers was studied in spring, summer and autumn of 2012 and 2013. The studies revealed the presence of 67 Rotifera species with their mean density ranging from 119 ind. dm-3 in Tomaszne lake to 1441 ind. dm-3 in Bikcze lake. Dominants included few very common species of Brachionus angularis, Keratella cochlearis, Keratella cochlearis tecta, Keratella quadrata, Polyartchra vulgaris. Dominance structure and species diversity suggest a slightly higher ecological status of Mytycze lake, as compared to the remaining eutrophic reservoirs. Faunistic differences observed among rotifer assemblages inhabiting individual lakes were significantly bigger than those registered in the successive study years within the area of individual lakes. This property referred to all the reservoirs, both the ones linked with the water system of the canal and the lakes not included in the canal system. Bigger faunistic differences occurred among rotifer assemblages inhabiting the lakes of Wieprz-Krzna Canal sys-tem, as compared with the assemblages found in the lakes not included in the system.