Occurrence and Distribution of Fecal Indicator Bacteria with Respect to Urban and Rural Land Uses

Abstract

There are many streams in Oklahoma that are vulnerable to fecal contamination from a variety of sources. The primary objective of this study was to determine the relative distribution of alternative indicator species such as Enterococci, Escherichia coli and Fecal Coliform as affected by land use (urban and rural), flow regime (high and low flow) and sample type (sediment and water column). The tests were conducted on Boomer and Cow Creeks, which are tributaries of Stillwater Creek, located in Stillwater, Oklahoma. The two locations on Boomer Creek represented urban land use, and the two on Cow Creek represented rural land use. There were also samples taken during baseflow and stormflow to compare microbial indicators during different flow regimes. Samples were processed using Enterolert method (Enterococci) and membrane filtration method (E. Coli and Fecal Coliform). Correlations were performed to understand the relationship between indicator organisms. The study provided insight on potential sources of fecal contamination. At all sampling sites, indicator organisms were detected at high density, especially during high flow and in sediments. There was not a consistent trend of greater densities of indicator organisms found in rural or urban areas. There was a consistent trend of E. coli and Enterococci violating recommended standards. In addition, strong correlations were found between E. coli, total fecal coliform and fecal coliform. The correlation between E. coli and total fecal coliform were highly significant suggesting that one organism may predict the other. Enterococci correlations were not significant with any of the coliforms.