Preliminary characteristics of the trophic condition of lakes located in the nature reserve "Beaver Sanctuary on the Pasłęka River".

Studied were the following lakes: Paslek, Wymoj, Sarąg, Łeguty and Isąg, located in the nature reserve “Beaver Sanctuary on the Pasleka River”. The hypothesis was that lakes located in a nature protection area are subject to eutrophication in a slow rate, however, the research did not confirm it. All lakes are very fertile, as shown by the concentrations of total nitrogen, total phosphorus, electrolytic conductivity and the high negative correlation between chlorophyll a and water transparency. In the peak of the summer stagnation oxygen profile is represented by the clinograde curve typical for eutrophic lakes while free carbon dioxide distribution in the water column is shown by a “reversed” clinograde curve, also typical for fertile reservoirs.