The Variability and Stability of Water Chemistry in a Deep Temperate Lake: Results of Long-Term Study of Eutrophication

Temporal and seasonal variability of hydrochemical properties in a deep, highly eutrophic lake was presented. It was shown that the feedback between the biocenosis and abiotic properties was of key importance for the lake environment, especially for features shaped by oxygen content. During vegetation season in a shallow trophogenic zone supersaturated with oxygen, quick depletion of some nutrients (mineral forms of nitrogen, phosphorus, and carbon) were noted. In a tropholytic zone, which constituted the major part of the lake water column, the mineralization of organic matter concentrations of mineral compounds were high. This layer was completely and permanently deoxygenated (anoxia). The reductive conditions intensified the release of biogenic compounds from bottom sediments. Many correlations between abiotic properties of water reflecting the complex interrelationships between biocenosis and biotope were stated. The relationship between photosynthesis and alkalinity and calcium distribution in the water column also was explained. On the basis of historical data (since the 1930s), tendencies of temporal changes in lake water chemistry were discussed as well as causes and effects of eutrophication.