Eutrophication of lakes - long-term changes

Pages 475-487 : illustrations ; 27 cm

No trends were found in longterm variation (between the 1970s and the 1990s) of basic trophic parametres (TP,TN, chlorophyll concentration, algal biomass, and water transparency) in five lakes of the river-lake system typical of a lakeland. hilly area (the Jorka river system, Masurian Lakeland). Recently, this lake chain maintains the historically developed trophic differentiation between deep, mesotrophic lake close to headwaters and shallow, eutrophic lake close to the outlet of the river. The only change found is the replacenemt of cyanobacteria dominating in the 1970s by dinoflagellates dominating in the 1990s. A strong correlation was found between TP loading to lakes and in-lake TP concentration in spring periods, however no correlation existed between TP and other trophic indices. On the other hand, the interrelations between SO, chlorophyll, and algal biomass were highly significant in summer periods and marginally significant in spring periods. This pattern was also found in other groups of lakes in the region. It is concluded that in hilly lakeland region, the river-lake systems draining small mosaic catchments are resistant to the further eutrophication (low nutrient loading, no point sources) and for this reason they tend to maintain the trophic conditions developed in the remote past.

Strony 475-487 : ilustracje ; 27 cm

Bibliografia na stronach 486-487

Bibliographical references (pages 486-487)