Chemical composition of the Tatra Mountain lakes:: Response to acidification

Data from two surveys of the Tatra Mountain lakes (Slovakia and Poland) performed in the autumns of 1984 (53 lakes) and 1993 or 1994 (92 lakes) were used to estimate spatial variability in water chemistry in this lake district during the period of maximum European acid deposition. The ionic content of the lakes was generally low, with conductivity (at 20 degrees C) ranging from 1.1 to 4.7 mS m(-1) and 23% of the lakes had a depleted carbonate buffering system. Major factors governing differences in the lake-water chemistry were bedrock composition and amount of soil and vegetation in their catchment areas. Compared to lakes in the predominantly granitic central part of the Tatra Mountains, lakes in the West Tatra Mountains had higher concentrations of base cations and alkalinity due to the presence of metamorphic rocks in the bedrock. Concentrations of phosphorus, organic carbon, organic nitrogen, and chlorophyll-a were highest in forest lakes and decreased with decreasing density of vegetation and soil cover in the catchment areas. Concentrations of nitrate showed an opposite trend. Several exceptions to these general patterns in chemical and biological composition were due to exceptional geology or hydrology of the lake catchments.