Hypertrophic Lakes and the Results of Their Restoration in Western Poland

Abstract

In this chapter we present our research on hypertrophic lakes and the identified changes in their water quality, phytoplankton and zooplankton, under the influence of restoration activities. Most of these lakes have been used for recreation, and – as a result of the deterioration of water quality – this option has lost. The average annual concentration of total phosphorus in almost all the lakes was higher than 100 μg/L, and the mean concentration of chlorophyll a was in the range of 40–172 μg/L, thus exceeding the limits for hypertrophy. To improve the water quality, so-called sustainable restoration was initiated, combining physical, chemical, and biological methods. Currently, we are documenting changes in the lakes Maltańskie, Uzarzewskie, Swarzędzkie, Rusałka, and Konin to verify the results of in-lake treatment. In the first four lakes, restored by phosphorus inactivation, oxygenation of water overlying the sediments, biomanipulation, and nitrate treatment of the hypolimnion, a gradual improvement of water quality was observed. This was manifested in phytoplankton community structure changes (less Cyanobacteria) as well as reduction in nutrient concentrations. In the case of Lake Konin, the inefficiency of EMs in lake restoration was noted.