In this work we tested biopreparations developed in our laboratory for their ability to degrade the organic matter of the bottom sediments of Turawa Lake. The biodegradation was conducted under laboratory conditions for 6 weeks. For the testing purposes, there were three variants of biopreparations that contained autochthonous strains originating from our own collection and their mixture. The testing showed that the introduction of the biopreparations to the bottom sediment resulted in a significant increase of the number of bacteria, which consequently brought about the reduction of organic compounds in the sediment. In the case of all the variants, the number of bacteria increased by order of 102 - 104 CFU/g after 42 days of biodegradation. Among the tested biopreparations, the most effective one was the mixture of the autochthonous strains and those originating from the collection. After biopreparation was applied, a drop of content of carbohydrates by 66.94%, fatty matter by 83.33% and proteins by 74.42% was noted.