Locational and temporal patterns in microorganisms potentially affecting water quality in the Dan River system

River ecosystems across the US and globally face numerous stressors that impact both ecological function and water quality. In 2015-16, municipalities along the Dan River in southern Virginia experienced repeated taste and odor (TandO) issues in their drinking water that originated from the river source water. Given that the source of TandO issues during these events were unknown, this research aimed to identify patterns in the distributions of river microorganisms that could help identify potential biological causes. Monthly water, sediment, and periphyton samples were collected for a full year from the Smith and Dan Rivers to quantify actinomycete, fungi, and chlorophyll a concentrations, which have historically been linked to TandO problems, and to characterize changes in microbial community structure. Although no significant TandO event occurred during the study period, the work produced unique and valuable data that describe patterns of microbial populations and communities in a river ecosystem. Results from the study show the abundances of actinomycetes, fungi, and chlorophyll a expressing seasonal and regional variation by habitat. From a broader ecological perspective, microbial communities sampled from water, sediment, and periphyton were each unique from each other regardless of river reach and season sampled. Overall, this research adds to our understanding of river ecology by detailing the microbial abundance and diversity in three river habitats, including periphyton, that can be used to predict sources of river TandO in future events, and offers new questions regarding how microbial diversity changes over space and time.