The paper presented the results of surface water temperature measurements from 17 lakes located in northern Poland and Belarus over the period of 50 years (1971–2020). Using the Excel computer program, Corel Quattro Pro 8, and graphic Draw 9, annual and monthly averages, extreme values, and annual and monthly trends were calculated and presented. These were supplemented by the monthly average air temperatures for 13 weather stations. The research showed that the temperature in all lakes was characterized by a positive trend at the level of 0.044 °C year⁻¹. The largest lake was characteristic for the Chervonoe Lake—0.066 °C year⁻¹—and the smallest 0.029 °C year⁻¹ for the deep Lake Hańcza. In the course of the average monthly surface water temperatures, a positive trend was also observed, ranging from 0.015 °C year⁻¹ in January to 0.069 °C year⁻¹ in May. These values correlated with the average air temperatures in the winter months (December–March) and with the winter NAO index (DJFM).

The investigation of lakes’ vulnerability to external impacts is essential for understanding and potentially mitigating the threats they face. By studying how lakes are affected by external factors, such as pollution, climate change and human activities, we can assess the health of the ecosystem and predict how it may respond to future changes. The purpose of this research is the analysis of climate change’s influence on the vulnerability of Belarusian lakes to external impact. The vulnerability indices were calculated using the randomized aggregate method. The dependences between parameters were defined on the basis of correlation and regression analysis. We investigated the vulnerability of 149 Belarusian lakes. Classifying the lakes allowed us to divide them into three types, with high, medium and low vulnerability to external impact. All the types include 2–3 subtypes. On the basis of classification, we created a zoning scheme for Belarus on the vulnerability of lakes to external impact. A forecast of lake vulnerability for three SSP scenarios to 2100 was conducted. In the SSP₁ scenario, the vulnerability of stratified lakes will increase insignificantly. The vulnerability of homothermous lakes will not change. In the SSP₂ scenario, the vulnerability of lakes will first increase then decrease. Lakes with high and medium vulnerability will be classed as medium- and low-vulnerable. In the SSP₅ scenario, the vulnerability of lakes will decrease more significantly than in the other scenarios.

Цель – анализ вертикального и горизонтального распределения температуры воды в озере Дол гое в период развития весеннего термобара 2024 г. Материалы и методы. В конце марта 2024 г. в ходе полевых исследований научно-исследовательской лабора тории озероведения БГУ были установлены закономерности пространственного распределения температуры воды в озере Долгое. Результаты полевых исследований сравнивались с результатами математического моделирования. Результаты и обсуждение. В результате установлено, что термобар в озере Долгое существовал с 26 по 31 марта 2024 г. Температура воды в этот период у берегов менялась от 4 до 8 ℃, в открытой части водоема – от 0,8 до 4 ℃. Моделирование физических процессов показало адекватное воспроизведение температур воды 30 31 марта 2024 г. в придонных слоях озера, в приповерхностных они были завышены относительно наблюдаемых на 0,5-1,4 ℃, что связано с отсутствием данных наблюдений 24-29 марта и недоучетом роли ветрового перемеши вания в формировании термической структуры озера Долгое. Южнее плеса с максимальной глубиной расчетные температуры занижены в связи с движением фронта термобара со всех мелководий, а не только со стороны про токи из озера Свядово. Выводы. Из-за мелководности по сравнению с озерами Байкал, Ладожским и др., а также ориентации длинной оси озера по направлению преобладающих ветров, прямая температурная стратификация до разрушения термоба ра в озере Долгое сформироваться не успела по причине очень быстрого потепления на фоне активного ветрового перемешивания. Температуры воды в приповерхностных слоях оказываются завышены, в придонных почти не отличаются от измеренных.

This article describes the reasons for and trends in the overgrowth of soft-water lakes in Belarus. Due to their unique water properties (low mineralization, pH, and nitrogen and phosphorus concentrations) and high water transparency, soft-water lakes are home to protected plant species like Lobelia dortmanna L., Isöetes lacustris L., and Littorella uniflora L. The purpose of this study was to analyze changes in aquatic vegetation distribution in seven soft-water Belarusian lakes and identify the causes of these changes. The initial data for this research were the results of field observations, the archive materials of the research laboratory of lake research conducted by the Belarusian State University for the period from 1971 to 2016, including morphometric and hydrochemical parameters, the characteristics of catchments and water exchange, and the results of studying the species composition and distribution of aquatic vegetation. The authors’ field studies were carried out in 2022–2024. We used expeditionary, hydrochemical, cartographic, and comparative research methods. The most significant changes in overgrowth were observed in Lakes Svityaz and Beloe (Luninets District). These lakes have high recreational loads. Significant negative trends were also noted in Lakes Bolshoe Ostrovito and Bredno. Over 35 years, the depth of distribution of submerged macrophytes in Lake Svityaz has decreased from 7 to 2 m, and the abundance and projective cover of semi-submerged macrophytes have increased. In Lake Beloe, I. lacustris, which forms a tier of submerged plants, has almost completely disappeared, and a previously absent strip of air-aquatic plants has formed. The total area of overgrowth in the lake has decreased from 35% of the water area to 3.2%. In Lake Bolshoe Ostrovito, Fontinalis sp., previously common at depths of up to 5 m, has practically disappeared. In Lake Bredno, the water moss Drepanocladus has spread to a depth of 4 m. In Lake Glubokoe, a new area of I. lacustris growth was discovered around an island at depths of up to 4 m. In Lake Cherbomyslo, the decrease in the species’ depth and area of distribution is associated with a weakening of the inflow of bog waters due to their backwater. The main causes of these changes are largely due to anthropogenic factors (water pollution by biogenic compounds) and, to a lesser extent, hydrological changes (decrease in the moisture content of lake catchments).