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The river ice regime is considered a sensitive indicator of climate change and within this study long term changes (in case of River Daugava starting from 1530, but for other studied rivers starting from first half of twentieth century) river ice regimes in the Baltic region have been studied. The ice cover duration on the rivers (17 rivers) in the Baltic countries and Belarus has decreased during the recent decades. In addition to this, long term observational records of ice break on the rivers of the studied region exhibit a pattern of periodic changes in the intensity of ice regime. Both the ice regime and the seasonal river discharge are shown to be strongly influenced by large-scale atmospheric circulation processes over North Atlantic that manifests through close correlation with North Atlantic Oscillation index.

The purpose of this study was to evaluate the level of heavy metal contamination of perch (Perca fluviatilis) from inland waters in Latvia. The level of metal (Cd, Cu, Co, Pb, Ni, Mn, Zn, Fe) accumulation in fish tissues (muscle, liver, and gills) relative to contamination level, gender, age, and tissue type were studied in fish samples from 14 bog (dystrophic) lakes and 23 lakes of different trophic status. Samples from some sites in the vicinity of the largest cities had significantly increased metal levels. In contrast, fish tissues from bog lakes had very low metal levels, possibly because of the high concentrations of natural organic matter in these waters.

The study of changes in river discharge is important for regionai climate variability characterization and for development of an efficient water resource management system. The hydrological regime of rivers and their long-term changes in Latvia were investigated. Four major types of river hydrological regimes, which depend on climatic and physicogeographic factors, were characterized. These factors are linked to the changes observed in river discharge. Periodic oscillations of discharge, and low-and high-water flow years are common for the major rivers in Latvia, A main frequency of river discharge regime changes of about 20 and 13 years was estimated for the studied rivers. A significant impact of climate variability on the river discharge regime has been found.

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