A spatial, multivariable approach for identifying proximate sources of Escherichia coli to Maumee Bay, Lake Erie, Ohio

Abstract

Abstract : Sources of E. coli at U.S. beaches are often unknown. Determining the spatial distribution of E. coli and identifying factors that can affect concentrations may provide insight into the sources of fecal contamination. This approach was used to investigate a popular bathing beach in northwest Ohio-Maumee Bay State Park (MBSP). In 2003 synoptic studies, water and bed-sediment samples were collected and analyzed for E. coli at 24 sites within Maumee Bay, a nearby shipping channel, a major tributary to the bay (Maumee River), and nearshore areas at the mouths of drainage ditches. In 2004, samples were collected at 22 sites identified as hot spots of fecal contamination during 2003. Daily samples for E. coli were collected at MBSP as part of the Ohio Bathing Beach Monitoring Program. Highest E. coli concentrations were found at sites in the Maumee River, the shipping channel, and in or at the mouth of some drainage ditches. These high values were found in bed sediments underlying the deepest waters, which may act as an E. coli sink. Low E. coli concentrations at sites remote to MBSP indicated that sources from these areas were not important contributors of E. coli. Temperature changes in discharge from a local powerplant did not cause an increase in E. coli concentrations. A ditch that discharges 75 m east of the bathing beach was shown to be a principal source of E. coli. Turbidity and rainfall were positively correlated with E. coli concentrations at MBSP. Higher wave heights and wind directions from the north, northeast, or northwest were associated with higher E. coli concentrations.