Factors affecting microbial community composition in Split Lake, MB, Canada

Split Lake is a large freshwater lake in northern Manitoba, Canada, that receives major inflows from the Nelson River, Burntwood River, and Grassy River. In 1976, during the Churchill River Diversion (CRD) project, most of the water in the Churchill River was diverted into the Nelson River via the Rat River, and the Burntwood River, creating a large inflow pressure in the lower Nelson area, including Split Lake. Decades after its implementation, the Churchill River Diversion still influences ecological and environmental processes in the area. In this study, metabarcoding of the 16S rRNA gene was employed to characterize the microbial community structure of the lake. Environmental factors (temperature, pH, turbidity, dissolved oxygen) and cyanotoxin levels were also assessed. The objectives of this study were to establish a baseline for microbiota across the lake and examine how environmental variables affect microbial population dynamics. The study was conducted in the summer of 2024, encompassing 14 sites on Split Lake and 2 sites on Assean Lake, an adjacent waterbody with minimal influence from hydroelectric infrastructure. Split Lake was found to harbor six distinct microbial clusters, with turbidity and dissolved oxygen levels correlating with different aquatic regimes within the lake. The predominant taxa in Split Lake included Actinobacteria hgcI clade and Cyanobium . Microcystin concentrations measured throughout the study were always below the Maximum Acceptable Concentration (MAC) set for Canadian federal drinking water standards.