It follows from the research conducted on the number of chitinolytic bacteria among planktonic and benthic bacteria that they occur in a higher number in bottom sediments than in water. However, the percentage of chitinolytic bacteria among the total number of heterotrophic bacteria was higher in the water than in the bottom sediments. Chitinolytic bacteria and the bacteria unable to decompose chitin most readily utilized N-acetyloglucosamine as additional sources of carbon and nitrogen. Chitinolytic bacteria developed well on a substrate with colloidal chitin as the only or an additional source of carbon and nitrogen. However, bacteria unable to decompose chitin displayed very weak growth on a substrate with colloidal chitin as the only source of carbon and nitrogen.