Escherichia coli and microbial source tracking marker concentrations in and near a constructed wetland in Maumee Bay State Park, Oregon, Ohio, 2015–16

Elevated Escherichia coli (E. coli) concentrations at the Maumee Bay State Park (MBSP) Lake Erie beach have resulted in frequent recreational water-quality advisories. After the construction of a wetland along Berger Ditch in Maumee Bay State Park, Oregon, Ohio, samples were collected and analyzed for concentrations of E. coli and microbial source tracking (MST) markers. This study was done by the U.S. Geological Survey, in cooperation with the University of Toledo, to provide data that can be used to help evaluate the effects of the wetland on water quality in MBSP. From July 2015 to February 2016, 116 samples were collected from six sites. Median GenBac (general marker) and E. coli concentrations were higher in samples from Berger Ditch sites than in samples from the wetland sites. No statistically significant difference was found between median E. coli concentrations in samples collected at Berger Ditch sites upstream and downstream from the wetland. The frequency of detection of the human-associated Bacteroides MST marker (HF183) decreased from 39 percent upstream from the wetland to 22 percent downstream from the wetland; however, the HF183 median concentrations from these two groups of samples were nearly the same (2,700 to 2,800 copies per 100 milliliters from upstream to downstream). The waterfowl-associated Helicobacter MST marker (GFD) was detected in 13 percent of samples from the Berger Ditch site upstream from the wetland, although it was not detected in samples from the Berger Ditch site downstream from the wetland. The ruminant-associated MST marker, Rum2Bac, was not detected at any site during this study.