EN
The study was focused on the analysis of the effect of the nutrient loads from cultivated and fertilized watershed on the ion balance in wetland ecotones. The investigations were carried out in Masurian Lakeland (NE Poland) in small (0.2 ha) fens dominated by cattail association. Wetland ecotones constitute an effective biogeochemical barrier in respect to nitrates. However, they do not protect lakes against other eutrophication factors arising as the result of multifunctional character of biogeochemical processes in the wetland environment under pression of nutrients of fertilizing origin. The eutrophication of waters can be enhanced by increased amounts of potassium, phosphates, and dissolved organic nitrogen moving out from wetland ecotones.