Abstract
Phosphorus release from bottom sediments studied in two zones of Lake Uzarzewskie differing in depth and water oxygenation displayed seasonal and spatial variability. The experiments indicated that the lake receives considerable internal loading, especially from the deeper, anaerobic, rarely-mixed part of the lake. Meanwhile, the shallow zone situated in the 0-3 m depth range, could be a sink for phosphorus during spring and a source during other seasons of the year. The total loading of phosphorus from the bottom sediments was over 950 kg year-1 P, and 83% of this amount originated from the deeper part of the lake. The mean release from this part was 24.89 mg m-2 d-1 P and the maximum in fall was 35.4 mg m-2 d-1 P.