VARIATION IN THE CONTENTS OF NITROGEN AND PHOSPHORUS IN THE HEATED WATER ECOSYSTEM OF THE KONIN LAKES
Jakub P. Pyka, Konrad Stawecki, Bogusław Zdanowski
Department of Hydrobiology, The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
ABSTRACT. The aim of the study was to determine changes in the trophic state of the Konin lakes heated water ecosystem. Changes in nitrogen and phosphorus content, Secchi disk visibility, and chlorophyll content were analyzed. The dominant form in the epilimnion was phosphorans and the organic fractions of the nutrients N and P. Phosphorans and ammonia nitrogen prevailed in the near-bottom layers and increased in the spring-summer period as oxygen deficits increased at the bottom. The deciding factor for eutrophication was nitrogen, the availability of which to phytoplankton was determined by the intensity of mineralization processes and denitrification. The short water retention time in the lakes restricted phytoplankton blooms. Phosphorus precipitation on calcite prevented lake eutrophication. The values of the TSISD and TSIChl indices were evidence of the mesotrophic status of lakes Licheńskie and Ślesińskie, while the TSIPtot index of phosphorus indicated a slightly higher degree of lake eutrophication.
Key words: HEATED WATERS, LAKE, EUTROPHICATION, NITROGEN, PHOSPHORUS, CHLOROPHYLL, WATER TRANSPARENCY