Investigation of Environmental Factors on Enterococcus Survival in Oklahoma Streams

In this study, we assessed six Oklahoma streams for Enterococcus sediment and water concentrations along with water quality, sediment, hydrologic and geographical factors. We also conducted a microcosm experiment from two stream sediments to evaluate Enterococcus survivability under stable laboratory conditions. Stream sites exhibited common relationships between Enterococcus and other environmental factors, including significant correlations to antecedent dry period, Escherichia coli , impervious area, dissolved oxygen, and turbidity. These correlations were found for Enterococcus in both water and sediment. Specifically for Enterococcus in sediment, concentrations were also significantly correlated to turbidity and sediment percent organic matter, but not to hydrological conditions. Conversely, concentrations of Enterococcus in water exhibited significant moderate correlations to precipitation, antecedent dry period, drainage area, impervious area, and discharge, as well as streambed particle size. High variability between geographical attributes and stream conditions increased uncertainties and relationships between Enterococcus concentrations in the stream among most factors. However, when grouping sites by similar watershed and sediment characteristics, strong significant relationships for water-quality parameters and Enterococcus concentrations in water and sediment were observed. The microcosm study indicated that sediment Enterococcus concentrations for two streams with contrasting sediment properties were stable, except for a considerable increase between day 0 and day 1, with no decay shown for a 31 day period. Collectively, our field and laboratory results revealed that Enterococcus can survive for extended periods under both dynamic and stable sediment and water conditions, and that environmental factors can be used to characterize freshwater streams and rivers for Enterococcus concentrations in freshwater streams and rivers.