The upper levels of salinity tolerance (assumed as 100% survival) after 48 h exposition were 12 and 13‰ in two the White Sea P. calkinski clones and 18‰ in one P. woodruffi clone from the Barents Sea coast. After carrying infusoria from the control medium (practically fresh water) into media of 8.5 and 12‰ salinity (P. calkinski) and 8.5 and 17(20)‰ (P. woodruffi) the rate of reproduction, intensity of phagocytosis and rate of contractile vacuole pulsation were determined. In all cases parameters of these major functions changed with oscillations in time and stabilized on the 5-8th days of the experiment. This fact suggests that these processes can be considered as adaptation in acclimation form.