On the basis of floristic analysis, the occurrence of 132 taxons of plankton algae in Koronowski Reservoir was determined. The spring and autumn plankton was dominated by diatoms, while summer plankton by blue-green algae. The species composition, structure of the abundance of algae and concentration of chlorophyll as well as physicochemical conditions of water suggested a highly eutrophic character of this reservoir with a starting expansion of blue-green algae, mainly species considered to be toxic.
M. Wisniewska, Academy of Technology and Agriculture, Faculty of Building Engineering and Environmental Engi-neering, Department of Environmental Management and Preservation, Sucha 9, 83-796 Bydgoszcz, Poland