Seasonal variability in phosphorus concentrations in strongly eutrophic Lake Chełmżyńskie

Abstract

Abstract:The results of the monthly examinations of Lake Chełmżyńskie carried out during the vegetation periods in the years 2007-2009 made it possible to define seasonal variability in the concentrations of phosphorus compounds. The examinations showed that the bottom deposits constitute a considerable source of phosphates. The release of phosphates from the deposits began as early as in mid May and with the occurrence of anoxic conditions. A particularly high concentration of phosphates in the near-bottom layer was recorded in the southeast pool of the lake (max. 0.658 mg P l [2007][2008][2009] showed that Lake Chełmżyńskie was classified as a strongly eutrophic lake. The ecological condition of the lake was defined as poor according to the Water Framework Directive. Reclamation works including the inactivation of phosphates in the bottom deposits are indispensable in order to improve the ecological and trophic state of the lake.