Microbial source tracking to elucidate the impact of land-use and physiochemical water quality on fecal contamination in a mixed land-use watershed

Escherichia coli has been widely used as a fecal indicator bacterium (FIB) for monitoring water quality in drinking water sources and recreational water. However, fecal contamination sources remain difficult to identify and mitigate, as mil-lions of cases of infectious diseases are reported yearly due to swimming and bathing in recreational water. The objec-tive of this study was to apply molecular techniques for microbial source tracking (MST) to identify sources of fecal contamination in a representative mixed land-use watershed located in the Appalachian Mountains of the United States of America (USA). Monthly samples were collected over one year at 11 sites, including the confluence of key first-order streams in the study watershed representing distinct land-use types and anticipated fecal sources. Results indicated that coupled monitoring of host-specific MST markers with the FIB E. coli effectively identified sources and quantified fecal contamination in the study watershed. Human-associated MST markers were abundant primarily at developed sites, suggesting septic or sewer failure is a key source of fecal input to the watershed. Across the dataset, samples positive for E. coli and human MST markers were associated with a higher pH than those samples from which each target was not detected, thereby suggesting that acid mine drainage in the watershed likely contributed to inac-tivation or loss of culturability in E. coli. In addition, this research provides the first evidence that the BacCan-UCD marker is present in fox feces and can influence MST results in areas where substantial wildlife activity is present. Iden-tifying the sources of fecal contamination and better understanding the impact of in-stream physiochemistry through-out this study will help to develop sustainable and effective watershed management plans to control fecal contamination to protect drinking water sources and recreational water.

Automated summary

In this study, molecular techniques were used to track the sources of fecal contamination in a mixed land-use watershed in the Appalachian Mountains. Results showed that human-related sources were primarily found in developed areas, indicating that septic or sewer failure is a major source of fecal input. Additionally, it was found that acid mine drainage may contribute to the inactivation or loss of culturability in E. coli. Identifying fecal contamination sources and understanding the impact of in-stream physiochemistry can help develop sustainable watershed management plans to protect water sources.