Extreme climate events are increasingly recognized as a threat to human health, agriculture, forestry and other sectors. To assess the occurrence and impacts of extreme climate events, we have investigated the changes of indexes characterizing positive and negative temperature extremes and extreme precipitation as well as the spatial heterogeneity of extreme climate events in Latvia. Trend analysis of long-term changes in the frequency of extreme climate events demonstrated a significant increase in the number of days with extremely high air temperatures and extreme precipitation, and a decrease in the number extremely cold days.

The sea ice regime is considered to be a sensitive indicator of climate change. This study investigates long-term changes in the ice regimes of the Gulf of Riga along the coast of Latvia in comparison with those of inland waters. The ice regime of the studied region indicates the impact of climate change related to increasing air and sea water temperatures. Ice cover duration on both the sea and inland waters has decreased during recent decades. In addition, long-term records on ice break in the studied region exhibit a pattern of periodic changes in the intensity of ice regime, while trends of the sea ice regime are not consistent between periods of time. Alternating mild and severe winters also occur. The ice regime was shown to be strongly influenced by large-scale atmospheric circulation processes over the North Atlantic, as indicated by close correlation with the North Atlantic Oscillation index.

Investigations of water chemical composition and biota of Lake Engure have been carried out since 1995 by using standard methods for inland surface waters. Time series of air temperature and precipitation for the Mersrags meteorological station for the period 1928 to 2009 are used for the trend analysis. The results show that the long-term development of the hydroecosystem is related to such environmental factors as the lake's geographical location, basin and morphology, as well as the lake's history and relationship of biotic and abiotic factors.

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Transformation into shallow lakes can be a major post-harvesting land-use option for cutaway peatlands. The aim of our study was to analyse factors influencing water quality and communities on lakes created in a cutaway bog in the Seda Mire, Latvia. The residual peat amount and the lake feeding conditions (the balance between ground water and inflow from adjacent river during the spring season) were found to be major factors influencing aquatic chemistry and studied habitats. The studied cutaway lakes cannot be considered as typical bog lakes regarding hydrochemical composition (especially regarding concentrations of major dissolved ions, pH and water colour) and hydrobiological features (metabolic activity, biomass and number of species of phytoplankton and zoobenthos). Considering aquatic chemistry and community structure of the cutaway lakes, a recommendation was made in respect to peat excavation to transform peat mining sites to lakes.