EN
The accomplished research covered the number and production of the heterotrophic bacteria colonizing the submerged surfaces of the two species of macrophytes: Common Reed (Phragmites australis (Cav.) Trin. ex Steudel) and Hornwort (Ceratophylhim demersum L.). These macrophytes predominate in the littoral zone of the Chelmżyńskie Lake. The ability of the bacteria to grow in the presence of different groups of amino acids and carbohydrates and decompose some biopoly- mers was determined. The greatest number and the highest production rate of the epiphytic bacteria were established to occur in the summer on the reed shoots. Amino acids and carbohydrates stimulated the development of bacteria isolated from the rigid hornwort's surface considerably more strongly; in turn, bacteria covering the reed shoots hydrolyzed macromolecular compounds to a greater degree.