Geoecosystems of Polish Lakes

This chapter contains an analysis of the geoecosystem types of 388 lakes of northern Poland determined by the method elaborated by E. Bajkiewicz-Grabowska, on the basis of data from the literature. The concept of lake geoecosystem is understood as a natural landscape system, composed of a lake with its catchment. The type of geoecosystem determines the rate of natural eutrophication of the reservoir’s water, and the rate is usually strongly modified by human activity. The method used to determine the geoecosystem type of a lake involves two elements: (1) the catchment as a supplier of matter to the lake and (2) the lake as a recipient of matter. Therefore, it considers the relationship between the lake and its alimentation area. It can therefore be used in different types of natural landscapes, and its core is the determination of (a) the vulnerability of the catchment to supplying matter into the lake, based on the properties of the physico-geographical environment of the catchment, and (b) lake resistance to the catchment impact determined on the basis of the limnological features of the lake. The combination of these two characteristics allows to distinguish four lake geoecosystem types with a specific natural eutrophication rate. It was shown that the majority (39%) of the analysed lakes have a geoecosystem of type 4 (low lake resistance to external pressure and high catchment vulnerability to supplying matter into the lake). The smallest group (18%) is composed of lakes representing geoecosystem of type 1, i.e. those characterized by low activity of the catchment in the supply of areal loads, as well as high lake resistance to external impact. The remaining lakes are characterized by a moderate eutrophication rate (geoecosystem of types 2 and 3).