Identifying spatiotemporal patterns and drivers of fecal indicator bacteria in an urban lake for water quality assessment and management

The designated uses of lakes connect individuals to the natural environment, but some can expose recreational users to pathogens associated with fecal contamination that cause waterborne illnesses. Routine monitoring of fecal indicators in surface waters helps identify and track sources of fecal contamination to protect public health. We examined fecal indicators (<i>Escherichia coli</i> and enterococci) and factors influencing recreational freshwater quality. We collected and analyzed water samples from an urban lake for 12 months to assess water quality. Fecal indicators were detected and enumerated using IDEXX method. <i>E. coli</i> and enterococci were detected in nearly 100 % of all water samples, but their concentrations varied significantly among seasons and land uses. We observed high levels of <i>E. coli</i> and enterococci during the warmer months. The geometric means of <i>E. coli</i> (28.5 MPN/100 mL) and enterococci (39.3 MPN/100 mL) were below and above the recreational water quality standards, respectively. The concentrations of <i>E. coli</i> (7 %) and enterococci (22 %) exceeded the recommended single-sample maximum levels. Sites near urban and forested areas recorded the highest and lowest fecal indicators, respectively. Water temperature, precipitation, salinity, resistivity, DO, and hardness were significant predictors of fecal indicators. The concentrations of fecal indicators were elevated at certain times of the year, indicating the potential presence of pathogens. Overall, the measured water quality parameters of the lake were within normal ranges. This study suggests that effective lake management should focus on the warmer months and runoff from urban and open space/agricultural areas to control nonpoint source pollution.