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Water chemistry in 280 small lakes in European Russia along a climatic transect from the Kola Peninsula (in the tundra and taiga zones) to the Caspian Lowland (in the arid zone) was investigated from 2000 to 2005. Here the chemical compositions of lake waters in different climatic ecoregions are characterised. Variability in water chemistry within and between ecozones is documented and discussed. The results show that within the humid zone, there was little variability in water chemistry and anthropogenic, geological and morphometric characteristics of lakes and their catchments had a strong effect on the chemical composition of waters compared to lakes in the arid and semi-arid zones. An estimation of the potential effect of climate warming on water chemistry showed that a temperature rise of 0.5-1 degrees C is likely to have no effect on major ion concentrations, whereas a temperature increase of 2 degrees C may lead to an increase of approximately 25% in total ion concentrations in the southern regions. Total P may increase approximately 50% in lakes throughout the study area if the average daily temperature were to increase by 0.5 degrees C. This would have an important effect on the nutrient status of these lakes. In particular, these processes are expected to be most pronounced in the arid zones. (C) 2012 Elsevier Ltd. All rights reserved.