Characterizing fecal contamination in stormwater runoff in coastal North Carolina, USA

Microbial contaminants in stormwater runoff have the potential to negatively impact public health. Stormwater runoff to coastal waters is increasing in amount and rate of discharge due to loss of vegetated landscape and increasing coastal development. However, the extent and nature of microbial contamination of stormwater runoff in North Carolina (NC) has not been previously characterized. The aim of this study was to measure a range of fecal indicator bacteria (FIB) and molecular markers at three coastal sites. E. coli and Enterococcus sp. were measured in addition to molecular markers including Bacteroides Human-Specific Marker (HS) and fecal Bacteroides spp. Levels of FIB in stormwater far exceeded recreational water quality guidelines, frequently by several orders of magnitude. High concentrations of fecal Bacteroides spp. and the presence of HS indicated the presence of human fecal contamination in the stormwater runoff, but only during specific storms. Examinations of levels of fecal contamination in stormwater over multiple seasons and a range of storm conditions will allow managers to consider appropriate design of effective mitigation strategies necessary to maintain and restore coastal water quality.