The presence of denitrifiers in bacterial communities of urban stormwater best management practices (BMPs)



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Stormwater best management practices (BMPs) are engineered structures that attempt to mitigate the impacts of stormwater, including nitrogen inputs from the surrounding drainage area. The goal of this study was to assess bacterial communities in different types of stormwater BMP in Clarksburg, MD to establish whether a particular BMP type could potentially harbor more denitrification potential. Sampling took place over the summer of 2015 following precipitation events. Four bioretention facilities, four dry ponds, and four surface sand filters were sampled. An additional single core was taken from one dry swale. Primers for the 16S rRNA gene as well as nirK, nirS, and nosZ denitrification genes were used for PCR amplification of DNA extracts prior to next-generation sequencing. RNA was also extracted to identify viable bacterial communities and was subjected to RT-PCR amplification using 16S rRNA primers. High bacterial diversity was evident in all BMP types sampled, including an abundance of denitrifiers. Based on the identification of a viable community of denitrifiers, denitrification could potentially occur under appropriate conditions in all types of BMP sampled, including surface sand filters that have tended to be ignored in these types of study. While surface sand filter media is predominantly inorganic material, the carbon content of incoming stormwater could be providing bacterial communities with conditions for denitrification. Overall, the BMPs sampled had a robust, diverse, bacterial community capable of denitrification.