Long term changes of phosphorus and nitrogen content and of trophic status in heated Konin lakes

Abstract

Basing on the content of phosphorus and nitrogen in water, on the Secchi disc visibility, on chlorophyll density and on primary production assessed in 1987 through 1992 the trophic status was described for 5 heated Konin lakes which differed with respect to limnological traits, annual flushing rate and phosphorus loading. The status depended on mineral fraction of phosphorus available to phytoplankton which in turn depended on the precipitation of phosphates and of calcium. An increase of phosphorus and nitrogen content as well as of the primary production in the most heated lakes over the recent years resulted from organic pollution.