Urbanization is one of the leading causes of stream degradation in the United States. Urban stormwater runoff carries many different pollutants that may affect the stream microbial communities, which play a crucial role in ecological processes such as decomposition of organic matter and recycling of nutrients. Stormwater retention ponds are the most common best management practices used in urban watershed to mitigate the impact of urbanization by delaying the runoff and reducing the pollutants from entering the stream. The objective of this study was to examine the influence of stormwater retention ponds on the downstream microbial community, specifically bacterial community. Water samples were collected from three urban streams above and below the retention pond and three least impacted forest streams (reference streams) in Potomac River watershed in north-east Virginia. Water quality parameters were analyzed and microbial communities were characterized by length heterogeneity-polymerase chain reaction (LH-PCR) of 16S ribosomal ribonucleic acid (rRNA).
Total suspended solid, nitrate-nitrogen, soluble reactive phosphate, and conductivity were generally lower downstream of the retention pond than upstream, although they were higher in urban streams than reference streams. Species richness and diversity of the bacterial community differed between upstream and downstream of the retention ponds with slightly higher richness and diversity downstream of the retention ponds. Reference streams had higher species richness and diversity compared to urban streams. LH-PCR analysis revealed that certain operational taxonomic units (OTUs) were specific to certain site (up and down of retention pond and reference) and water quality parameters, suggesting that changes in environmental conditions caused by the retention pond influenced the bacterial community structure of the site.