Escherichia coli and Enterococci Bacteria in Lake Michigan Beach Sand

Abstract

Fecal indicator bacteria can be used as a surrogate to pathogenic microorganisms to monitor fecal contamination in water bodies. Increased concentrations of fecal bacteria may pose public health risks associated with swimming and other recreational activities at beach sites. This study was carried out during the summer and early fall of 2013 to monitor Escherichia coli and Enterococci as indicator bacteria at Bradford Beach, along the shoreline of Lake Michigan in Milwaukee, WI. Enumeration of bacteria in beach sand and water samples was performed using the IDEXX Most Probable Number method. Deionized (DI) water and phosphate-buffered saline (PBS) were used as the eluents for bacterial enumeration. The EPAs CANARY event detection software was used to analyze bacterial concentrations and identify anomalous water quality events. CANARY was deemed to be a useful statistical tool for analyzing fecal indicator bacteria concentration and providing timely information on beach contamination to reduce public health risks associated with pathogens. The model results indicate that beach sand can act as a potential reservoir for bacteria to survive longer than in water. In addition, the concentration of E. coli enumerated in DI water was higher than in PBS. The analysis of E. coli concentration in beach sand indicates the possibility of establishing a relationship between the results obtained using the two eluents. Furthermore, a correlation between the algal level and bacterial count was identified. The results from the CANARY software indicate that the presence of algae has a significant impact on the bacterial concentration.