Abstract
The aim of the study was to identify changes in the quality and quantity structure of the zoobenthos assemblages inhabiting the lakes, channels, and basins that comprise the cooling system of a power plant in central Poland. By comparing the invertebrate fauna occurring on the freshwater clam Sinanodonta woodiana (Lea) and the macrophyte Vallisneria spiralis (L.), the significance of exotic species in the development of invertebrate macrofauna species was demonstrated. The zoobenthos inhabiting the channels was poorer quantitatively and qualitatively than was the lake zoobenthos. Factors that determined this included thermal and oxygen conditions and water flow. Elements that enriched the development of the zoobenthos and the zooperyphyton included populations of alien zebra mussel Dreissena polymorpha Pallas and S. woodiana, and assemblages of Myriophyllum spicatum L. and Ceratophylum demersum L. In comparison to thirty years ago, the quality of the bottom fauna in the system has decreased.