The microbiological activity of lake sediments before and after application of EM (effective microorganisms)

The study objective was to assess microbiological activity of sediments during the application of an EM preparation on the in Lake Skiertąg. Samples were taken before and after microbial bioremediation in the period 2020–2021 from five sediment layers. The abundance, biomass, and efficiency of the respiratory chain of sediment bacteria were determined by the direct methods in a fluorescence microscope. The rate of organic carbon oxidation was measured by the respiratory method. The abundance of benthic bacteria showed significant variability in the profile of each core, and decreased with an increase in sediment depth. The significant decrease in the number and biomass of bacteria in the sediment after the application of the EM technology, was observed during the second year of application of the preparation, and not immediately after its application. In the tested sediments, an significant increase in the percentage of cell with active dehydrogenases ETS+ in the total number of bacteria after application of the preparation was found, but at the same time significantly higher values of this parameter were demonstrated in 2021 compared to the first year of using microbial bioremediation. A significant positive correlation between the potential rate of organic carbon oxidation in the surface layer of sediments and the temperature in the water above the sediment indicates that the temperature conditions stimulated the respiration activity of the sediment microflora.