CLIMATE CHANGE IN THE LOW DNIESTER BASIN AS A FACTOR OF IMPACTS ON WATER ECOSYSTEMS

Abstract

Problem. Obviously, the biotic composition, structure and function of freshwater ecosystems depend largely on the climatic conditions in a river basin. This dependence becomes more complicated in the context of global warming, when the centuries-old relative climate stability, or its stationarity, disappears, and the more and more increasing changes in climate are observed. Aim. The aim of the present research was to compare statistically temperature-humidity conditions in the Low Dniester basin in two periods (1961-1990 and 1991-2018) that respectively characterize different climatic thirty-years according to the WMO classification.Methods. For each period, the average annual and seasonal values of key climatic variables - air temperature and precipitation - as well as their linear trends were considered. As initial information, the observations at weather stations of Moldova, located in this part of the Dniester basin, were takenResults. The analysis showed that in the second periods the annual mean (Tmean), maximal (Tmax) and minimal (Tmin) temperatures have increased in absolute terms by 1.0, 1.8 and 0.7°C, respectively. With regard to seasonal temperatures, the highest Tmean increase was observed in summer (1.6°C), the smallest – in autumn (0.4°C). Tmax increased mostly in winter (by 3.1°C), and to a lesser extent – in autumn (by 0.6°C). The greatest increase in Tmin was observed in winter (1.7°C), the smallest – in spring (0.2°C). At the same time, the total change of precipitation was extremely small: only 6 mm decrease per year. A slight increase in precipitation (by 25 mm) was noted only in the autumn months. The analysis of linear trends confirmed the results of a comparative analysis. Negative air temperature trends in 1961-1990, with the exception of a slight positive one for Tmax, have changed to their positive values for all parameters in the last three decades. In particular, during this period the increase in mean air temperature was 0.6°C per decade. The slight negative trend of precipitation (~2 mm/year) in 1961-1990 was replaced by their negligible increase (~0.5 mm/year).Conclusion. An increase in air temperature, which is not compensated by an increase in precipitation, is inevitably accompanied by an increase in the climate aridity, already characteristic for the northern Black Sea coast, which negatively affects the existence and development of aquatic and terrestrial ecosystems in this region.