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This paper offers a synthetic account of selected hydrological and physical characteristics of two coastal lakes in Poland, under the apparent influence of changes to be observed in elements of climate. The focus was on those characteristics whose changes can affect lake morphometry and water resources significantly. The two coastal lakes in Poland selected for study were Lakes Gardno and Łebsko, both of which are situated in the area of Słowiński National Park. To achieve the objective, it was necessary to analyse the parameters shaping the lakes’ resources, also as a reflection of their respective positions in the catchment of, and in hydraulic connectivity with, the main drainage base, i.e. that of the Baltic Sea. The parameters characterised were therefore: precipitation, potamic inflow, lake levels and fluctuations in levels, and seaward alimentation. All of these aspects were considered in relation to the 50-year period of 1961‑2010. The study also considered processes occurring in the lake basins themselves (surface changes, shallowing), as well as physical properties of the water (temperature, ice). In the event, it emerged that the work was unable to establish unequivocally the directions in which the two studied lakes could be thought to be evolving. There are nevertheless many indications that the anticipated process of transformation over a geological timescale will be accelerated, resulting in the final (disappearance) stage being reached much faster than would be expected from the natural, harmonic process of ageing of lakes. Leaving aside the fact of human influence in the context, many studied parameters describing the hydrological and physical properties of the two lakes could be regarded as manifesting trends correlated with global warming. On the one hand, the recorded increases in potassium inflows equal to 0.20 m³ ·s-1/10 years (along the River Łupawa) and 0.27 m³ ·s-1/10 years (along the River Łeba), as well as in sea level (equal to 1.6‑1.8 cm/10 years), offer a guarantee of stable water resources forming in the lakes, and should denote increased water levels. In the event, however, the research actually shows the two lakes reacting differently to supply, to the extent that the negative trend for water level in Lake Gardno (of -0.17 cm/10 years) contrasts with the positive one noted for Lake Łebsko (equal to 1.40 cm/10 years). On the other hand, volumes of water retained naturally could be expected to be impaired by observed increases in air temperature – and consequently water temperature, as well as frequently occurring droughts, increased water losses due to evaporation, and unfavourable morphometric features of the lakes. Furthermore, increased supply of sediments by rivers as a consequence of increased flow would be expected to bring about reductions in area, with faster overgrowth taking place. Reed communities at present occupy 4.1% of Lake Gardno and 9.1% of Lake Łebsko. Since 1836, the lakes are estimated to have shrunk by some 237 ha (9.1%) in the case of Lake Gardno, and 546 ha (7.2%) in the case of Lake Łebsko. Meanwhile, positive trends for water temperature in both lakes resulted in a decline in the number of days with ice phenomena over the 50-year study period – from over 100 to just 50‑60. [ABSTRACT FROM AUTHOR]

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