The oxygen budget of two closed, dimictic lakes in the vicinity of Bytów (West Pomeranian Lake District, northern Poland)

The aim of this work was to identify key factors governing the oxygen fluxes in two thermally stratified lakes of different morphology. Oxygen and temperature profiles in lakes Jeleń and Mały Borek, as well as phytoplankton primary production in Mały Borek (oxygen-method) were measured in monthly intervals, except for periods of ice cover. Rates of oxygen release due to photosynthesis, consumption in the water column, loss to atmosphere, depletion in the hypolimnion, and restoration during periods of turn-over were roughly estimated. It was discovered that trophic conditions and morphometry may substantially influence not only the intensity, but also the timing, of particular events in the oxygen cycle of the lakes.