EN
The occurrence of bacteria displaying particular physiological properties was studied in polluted (Sopot) and unpolluted (Czołpino) marine sandy beaches (southern Baltic Sea). All eight isolated physiological groups of bacteria were much more numerous in polluted than in unpolluted beach. In polluted beach, bacteria hydrolyzing uric acid (32.5 cells 103 g–1 dry w. of sand) and ammonifying bacteria (32.3 cells 103 g–1 dry w. of sand) were the most numerous, while nitrifying bacteria were the least numerous (0.014 cells 103 g–1 dry w. of sand). In unpolluted beach, bacteria hydrolyzing uric acid (0.66 cells 103 g–1 dry w. of sand) and reducing methylene blue (0.18 cells 103 g–1 dry w. of sand) were the most numerous, while no bacteria producing hydrogen sulphide from organic compounds or bacteria decomposing urea were isolated. In both beaches, considerable differentiation in the distribution of physiological groups of bacteria was found in a horizontal profile i.e. from the waterline to the middle of beach (~60 m). Data concerning horizontal distribution of the physiological groups of bacteria in the sand of the polluted beach show that the majority of those groups was most numerous in the dune. No clear regularity in the distribution of physiological groups of bacteria was found in the horizontal profile of the unpolluted beach. Results of the present study indicate differences in the distribution of the physiological groups of bacteria in the surface (0–5 cm) and subsurface (5–10 cm) sand layers. Generally, in both studied beaches all physiological groups of bacteria were much more numerous in the surface than in the subsurface sand layer. The exception were bacteria reducing sulphates which in the polluted beach were most numerous at the depth of 5–10 cm.