COMPOSITION AND DISTRIBUTION OF EPIPHYTIC MIDGES (DIPTERA: CHIRONOMIDAE) IN RELATION TO EMERGENT MACROPHYTES COVER IN SHALLOW LAKES

The influence of emergent macrophytes (dominated by Phragmites australis (Cav.) Trin. ex Steud.) on the species composition, richness and abundance of epiphytic midges (Diptera: Chironomidae) was studied in five shallow lakes of eastern Poland during three seasons (May, July and October) of 2001. The lakes represented three states: clear (macrophyte dominated), intermediate (phytoplankton-macrophyte dominated) and turbid (phytoplankton dominated). The trophic status of lake strongly affected the assemblages of chironomids living on the surfaces of common reed. Habitat conditions regulated mostly densities and relative abundance of midge taxa and did not have any significant influence on the number of taxa. The Canonical Correspondence Analysis of epiphytic fauna showed the significance of 5 environmental variables: Secchi disc visibility, dissolved oxygen, reed density, concentration of total phosphorous and epiphytic chlorophyll-a. The analysis separated epiphytic midges into two groups. The first group included taxa limited by low oxygen content and water transparency and corresponds with clear state habitats. To the second group belong taxa typical of eutrophic waters with densities determined by the concentrations of total phosphorous and chlorophyll-a, common in lakes of intermediate state and in particular of turbid state.