EN
The investigations were carried out in the region of Rabka, a well-known health resort, situated in a valley between the ranges of the Wyspowy Beskid and Gorce Mts (The Carpathians), on the River Raba. The Poniczanka stream which is a tributary of the River Raba has recently undergone investigation. This is a stream in which the presence of a very rare species of the P. aurelia complex, i.e. Paramecium tetraurelia, was found in 1961 (DUBIS, unpublished data). The present study revealed a significant acidification of the stream and the absence of the Paramecium tetraurelia. Among the species of the genus Paramecium only Paramecium caudatum was found, this morphological species, composed of several genetic ones, seems to be less sensitive to acid waters.