Fecal pollution source characterization at non-point source impacted beaches under dry and wet weather conditions

• Published in: Water research (Oxford) Vol. 182; p. 116014
• Main Authors: Shrestha, Abhilasha, Kelty, Catherine A., Sivaganesan, Mano, Shanks, Orin C., Dorevitch, Samuel
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-09-2020
• Subjects: Fecal indicator bacteria; Microbial source tracking; Non-point source pollution; Precipitation; qPCR; Recreational water quality; Recreational water quality; Precipitation; Non-point source pollution; qPCR; Microbial source tracking; Fecal indicator bacteria
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2020.116014

Though Lake Michigan beaches in Chicago are not impacted by stormwater or wastewater outfalls, several of those beaches often exceed USEPA Beach Action Values (BAVs). We investigated the role of microbial source tracking (MST) as a complement to routine beach monitoring at Chicago beaches. In summer 2016, water samples from nine Chicago beaches were analyzed for E. coli by culture and enterococci by qPCR. A total of 195 archived samples were then tested for human (HF183/BacR287, HumM2), canine (DG3, DG37), and avian (GFD) microbial source tracking (MST) markers. Associations between MST and general fecal indicator bacteria (FIB) measures were evaluated and stratified based on wet and dry weather definitions. Among the 195 samples, HF183/BacR287 was quantifiable in 4%, HumM2 in 1%, DG3 in 6%, DG37 in 2%, and GFD in 23%. The one beach with a dog area was far more likely to have DG3 present in the quantifiable range than other beaches. Exceedance of general FIB BAVs increased the odds of human, dog and avian marker detection. MST marker weighted-average fecal scores for DG3 was 2.4 times, DG37 was 2.1 times, and GFD was 1.6 times higher during wet compared to dry weather conditions. HF183/BacR287 weighted-average fecal scores were not associated with precipitation. Associations between FIB BAV exceedance and MST marker detection were generally stronger in wet weather. Incorporating MST testing into routine beach water monitoring can provide information that beach managers can use when developing protection plans for beaches not impacted by point sources.
•Exceedance of BAVs is associated with higher odds of dog and bird marker detection.•Dog markers were more likely to be detected following precipitation.•MST findings coupled with precipitation information can guide beach management.•MST can provide actionable information as a supplement to routine beach monitoring.