The investigations regarded a holomictic Lake Wulpińskie located near Olsztyn. Samples were taken during the autumn circulation 2007 and spring circulation 2008 over the deepest site of each of the bay and compared to previous data. The lake consists of two parts: eumictic tomaszkowska (459 ha, 22 m), and bradymictic barwińska (246 ha, 54.6 m), separated by an inlet with a length of about 60 m and depth 3.8 m. Subcatchments both of bays vary in size and the way of use. Tomaszkowska is more vulnerable to tourist pressure and 62.7% used of agriculture, while the fields and meadows in subcatchment of Barwińska constitute 46.3%. This was reflected in the findings obtained: tomaszkowska has lower visibility of Secchi disc (1.5–1.75 m), higher chlorophyll a concentration (23.25– –26.19 mg ∙ m^–3) and pheophytin (60.11–64.77 mg ∙ m^–3), a larger amount of allochthonous matter and a clear upward trend of this parameter in the deepest part of water. The total nitrogen pool was dominated by organic form.

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