Analyses of Kings Creek Water and Watershed Runoff Samples for Bacteroidales using qPCR to Detect Human Fecal Contamination

Summary: The purpose of this work was to evaluate and analyze water samples collected from the Kings Creek watershed using a qPCR-based method to detect both total Bacteroidales and Bacteroidales reported to be associated with human fecal contamination. Quantitative real-time PCR assays were used to significantly reduce processing times and at the same time yield estimates of target concentrations. Initial efforts focused on evaluation of various Bacteroidales primer sets reported in the literature tested against human and animal fecal samples collected from the Kings Creek watershed. Most samples, both animal and human, were positive with the universal (i.e. general or total) Bacteroidales assay. Strong positive signals were found with human sewage using the human-specific assay that was chosen for this study. Most animal scat samples were negative with respect to the human-specific Bacteroidales indicator. The few animal samples that were positive with the human-specific assay had very low signal intensity. Despite the generally pervasive drought conditions during this study, evidence of human contamination was detected at certain feeder stream locations, and was widespread after a significant rain event that occurred in late fall. Use of the human-specific Bacteroidales indicator holds promise as a tool to identify potential human, as opposed to animal, sources of contamination but will require a more comprehensive field monitoring and sample collection effort than could be managed in this preliminary study