ERP139919 PRJEB55053 2a01051a-be82-4c4b-b319-5bb2c91ab445 Stimulation of hydrocarbons biodegradation in sediments Historical contamination of freshwater lakes with hydrocarbons (HC) due to anthropogenic activities represents a serious problem worldwide. One of the most realistic technological solutions in that case is the stimulation of biodegradation processes by ex situ remediation of lake sediments (LS). The present study was aimed at evaluating the effect of bio-stimulation and bioaugmentation on the biodegradation of hydrocarbons in LS, as well as changes in microbial community structure and metabolic activity. The concentration of HC in LS during the 32-day incubation decreased in average from 465 mg/kg to 165 mg/kg and 117.5 mg/kg in the LS amended with nutrients and nutrients+bacterial consortium, respectively. Different treatment types of LS resulted in differences in microbial respiration and HC-degrading activity. The Shotgun sequencing has revealed the main phyla present in the intact LS being Proteobacteria (48.8%), Actinobacteria (24.4%), Firmicutes (10.4%) and Bacteroidetes (5.0%). Incubation of LS for 32 days resulted in increasing abundance of Proteobacteria from 48.8% in the raw LS to 58–62%, mainly due to the increase of Betaproteobacteria. The functional annotation of gene families, as well as metabolic biodiversity of culturable microorganisms was analyzed. Effect of treatments on the abundance of diatoms in LS was analyzed. The data obtained in this study indicated that the suggested approach is a potent remediation technology for further ex situ scaling up. Ex situ stimulation of hydrocarbons biodegradation in freshwater sediments from historically contaminated Aluksne lake Historical contamination of freshwater lakes with hydrocarbons (HC) due to anthropogenic activities represents a serious problem worldwide. One of the most realistic technological solutions in that case is the stimulation of biodegradation processes by ex situ remediation of lake sediments (LS). The present study was aimed at evaluating the effect of bio-stimulation and bioaugmentation on the biodegradation of hydrocarbons in LS, as well as changes in microbial community structure and metabolic activity. The concentration of HC in LS during the 32-day incubation decreased in average from 465 mg/kg to 165 mg/kg and 117.5 mg/kg in the LS amended with nutrients and nutrients+bacterial consortium, respectively. Different treatment types of LS resulted in differences in microbial respiration and HC-degrading activity. The Shotgun sequencing has revealed the main phyla present in the intact LS being Proteobacteria (48.8%), Actinobacteria (24.4%), Firmicutes (10.4%) and Bacteroidetes (5.0%). Incubation of LS for 32 days resulted in increasing abundance of Proteobacteria from 48.8% in the raw LS to 58–62%, mainly due to the increase of Betaproteobacteria. The functional annotation of gene families, as well as metabolic biodiversity of culturable microorganisms was analyzed. Effect of treatments on the abundance of diatoms in LS was analyzed. The data obtained in this study indicated that the suggested approach is a potent remediation technology for further ex situ scaling up. ENA-FIRST-PUBLIC 2022-07-29 ENA-LAST-UPDATE 2022-07-29