Rainfall Influences on Microbial Community Dynamics in an Urban Watershed

Abstract

Cameron Run and Hunting Creek are two freshwater tidal embayments of the Potomac River, located downstream of wastewater treatment facilities. During heavy rainfall events, the combined sewage system near Cameron Run results in rainwater and domestic sewage overflowing into the nearby watershed. Microbial communities were characterized and compared over different levels of precipitation and other environmental parameters to identify possible biological indicators for water quality and aquatic health. A 16S rRNA gene amplicon sequencing approach was used to identify potential microbial biomarkers of environmental disturbance. We collected river water from different sites along Cameron Run and Hunting Creek and characterized microbial populations present over a four-month time period. We found a high quantity of Bacteroides present across all sites, potentially indicating fecal contamination. Species richness and community structure were significantly influenced by rainfall and temperature. In particular, the relative abundances of genera Devosia (a nitrogen-fixing soil bacterium), Sphingomonas, and Arthrobacter (commonly found in soil) were correlated with higher rainfall. Further analysis of this multi-year data set will seek to uncover additional microbial indicators by examining fluctuations in the microbial community related to changes in specific environmental parameters over time.