Stream Biofilms in Western Tennessee Provide Insight into Land Use History and Ecosystem Function

Many streams in western Tennessee (United States) are heavily modified, altering stream morphology and microbial community dynamics. Given the interest in restoring degraded streams, integration of microbial communities and processes is needed to inform restoration efforts. We investigated community assembly dynamics of biofilm microbial communities in a degraded and undisturbed stream within the same watershed; the degraded stream is scheduled to be restored. We established biofilm sampling plots, which included the factors light exposure, length of biofilm development, and temporal variation. We conducted metabarcoding targeting bacteria and eukaryotes, investigating community dynamics of 13 functional or taxonomic groups. We also collected stream chemical data including pH, dissolved oxygen, oxygen reduction potential, total dissolved solids, K+, NO3−, electrical conductivity, and temperature. We observed greater diversity and higher abundances in the more natural stream, but these patterns are taxonomically context-dependent. Using a community assembly analytical framework, we identified strong temporal effects of community structure and stream chemistry. These dynamics also highlighted biomarkers that are potential indicators of stream conditions. This work highlights the need to integrate aquatic microbial communities into conversations around stream restoration.