Valero, Anna Maria2025-04-072025-04-072025-04-072025-04-02https://hdl.handle.net/10012/21565Climate change is exacerbating landscape disturbances such as wildfires, which are becoming larger and more severe. When wildfires are coupled with precipitation, nitrogen and phosphorus from runoff can cause eutrophication of water systems. More severe wildfires can have prolonged impacts on drinking water sources due to internal loading of nutrients from sediments, sustaining eutrophic conditions. Furthermore, eutrophication of water systems increases the susceptibility of cyanobacterial proliferation in aquatic systems, which can have negative impacts on the quality of drinking water sources. Cyanobacteria can impact drinking water quality by producing toxins that impact human health, as well as produce taste and odour compounds that influence the perception of safe drinking water. Sustained eutrophic conditions due to wildfires makes aquatic systems vulnerable to reoccurring cyanobacterial blooms, and this creates challenges to drinking water treatment processes and in turn, impacts drinking water security. In 2016, the city of Fort McMurray was impacted by the Horse River wildfire that devasted the community and the surrounding watershed. Although only 5-6% of the Athabasca watershed was impacted by the wildfire, much of the area upstream of the Fort McMurray WTP was affected. Effects of this wildfire are still prevalent in the city’s source water seven years after the wildfire. Notably, cyanobacterial blooms have occurred every year since the fire. While these blooms have not affected the quality of treated and distributed drinking water, the potential for production of toxins that cannot be treated with current technologies available in the water treatment plant remains. The possible role the benthic bacterial communities play in internal loading of nutrients and distribution of benthic cyanobacterial communities have yet to be investigated within Fort McMurray untreated source water reservoirs. This thesis investigated the spatial and temporal patterns of benthic bacterial and cyanobacterial communities monthly (June-September 2023) from sediments and water from the water-sediment interface from an untreated drinking water source reservoir in Fort McMurray and from the Snye, a channel off the Clearwater River. This was done by sequencing of the 16S rRNA gene of DNA extracts and using QIIME2 for bioinformatic analyses. There were temporal changes in bacterial communities in benthic water, such as increases in phylum Cyanobacteriota in August, indicating cyanobacterial blooms not being unique to a specific water body in Fort McMurray. Bacterial communities in sediments were more stable than benthic water across the seasonal period at both locations. The cyanobacterial genus Aphanizomenon was detected in the benthos over the seasonal period and can pose challenges in drinking water reservoirs as members of this genus are potentially toxic, bloom-forming cyanobacteria. Cyanobacterial communities are often overlooked in the benthos, therefore, monitoring the distribution of potentially toxic cyanobacteria that can form reoccurring blooms in drinking water sources is advantageous in protecting drinking water security. Gene abundance for enzymes involved in the cycling of bioavailable phosphorus and nitrogen, limiting nutrients to cyanobacteria, were predicted for bacterial communities of benthic water and sediment from August 2023 from an untreated drinking water source reservoir within Fort McMurray and the Snye. This prediction was done using 16S rRNA gene sequencing data and the PICRUSt2 software. Bacterial communities were predicted to have a higher gene abundance for enzymes involved in bioavailable phosphorus cycling than nitrogen cycling. Detecting bacterial orders which are top contributors to the predicted gene abundance in phosphorus and nitrogen cycling can highlight the ecological risk to account for in nutrient release and management in the benthos. Sediments are critical in cyanobacterial bloom dynamics in areas impacted by wildfires and should be factored in the delayed recovery of untreated source water reservoirs from a nutrient-rich state. Cyanobacterial blooms are global phenomena with occurrences increasing due to the declining number of oligotrophic systems and sustained eutrophic conditions, which wildfires play a role in. Understanding the distribution of cyanobacteria in untreated source water reservoirs and possible bacterial nutrient cycling aid in the assessment of risk in monitoring programs and mitigation of cyanobacterial blooms by nutrient management. Wholistically investigating raw/untreated water supplies by including analysis of benthic bacterial communities is important in protecting drinking water security, especially in areas impacted by wildfires.enalgal bloomsforest firescyanobacteriasedimentamplicon sequencingnutrient cyclingeutrophicclimate changeMaster Thesis