Plankton Communities in Oxbow Lakes of the River Vistula (Oświęcim Basin) with Bottom Sediments Heterogeneously Contaminated with Heavy Metals

This study presents plankton communities (phytoplankton and zooplankton) in the three reservoirs of the River Vistula’s oxbow lake near Zator (Oświęcim Basin). Selected physicochemical parameters of the oxbow lake waters and the bottom sediments were analysed. Aquatic ecosystems in the investigated area have been heterogeneously contaminated with heavy metals (mostly by zinc, cadmium, lead and chromium), because of contaminated waters of the Vistula, and with manganese and iron. The highest differences were observed between Krajskie and Miejsce oxbow lakes among chlorides and the conductivity of the water and among Cr and Fe in the bottom sediments. This indicates a strong influence of the River Vistula. The plankton structure was different in each of the oxbow lakes. The index of taxa similarity showed also differences in the structure of plankton in oxbow lakes, which was convergent with the chemical parameters of oxbow lakes. The index of taxa similarity was similar for all three oxbow lakes only for one group of algae (Chlorophyta) and one group of plankton animals (Rotatoria). Lower similarity was shown between one oxbow lake impacted by the River Vistula (Krajskie) and another oxbow lake completely separated from the River Vistula (Oko).