This study presents results of research on a number of microorganisms in soil of the Chełmżyńskie lake watershed and their role in the decomposition of chitin. The authors also examined the level of respiration activity of soil in the presence of shrimp waste. Results demonstrate that the number of microorganisms in soil were variable. During the entire research period, the analyzed groups of microorganisms predominated in ploughland soils with the number of heterotrophic bacteria significantly exceeding that of actinomyces and fungi. The proportion of microorganisms capable of decomposing chitin was greater among actinomycetes and fungi than among heterotrophic bacteria. Chitinolytic bacteria constituted 15-25% of the total number of heterotrophic bacteria and their proportion was higher in sandy soil. Chitinolytic fungi constituted 29-42% and also dominated in sandy soil. Chitinolytic actinomycetes constituted 48-69% and also dominated in sandy soil. The level of respiration activity soil statistically depended on examined factors. Respiratory activity was highest at 24ºC (in summer) and lowest at 6ºC (in spring). During the entire research period, the microorganisms inhabiting sandy soil were more readily able to take advantage of shrimp waste and found shrimp heads the most useful, shells the least useful.