Assessment of Fecal Coliform and Escherichia Coli Across a Land Cover Gradient in West Georgia Streams

Abstract

Conversion of forested land to suburban and urbanized landscapes is occurring at extreme rates, especially in the southeastern United States. To examine the effects of land cover on bacteria indicator concentrations in streams, twenty small watersheds (<2500 ha) within the Middle Chattahoochee Watershed of western Georgia were chosen for investigation. Watersheds were selected to represent a gradient of impervious surface cover and also to represent a wide array of land covers, including urban, developing, pastoral, mixed species forests, and pine forests. Grab samples were collected from May 2002 to January 2006 and analyzed for fecal indicator bacteria, ammonium, nitrate, phosphorus, and total suspended solids. In general, urban watersheds revealed higher concentrations of fecal coliforms and Escherichia coli than other land covers. Fecal indicator bacteria concentrations and violations of bacteria state and federal standards were positively correlated with percent impervious surfaces. Furthermore, positive relationships between fecal indicator bacteria and ammonium and total suspended solids were found during stormflow. These results suggest that watershed land cover may impact the period of time that waters exceed the fecal coliform and E. coli standards. Additionally, these data reveal that the fecal coliform review criterion may be met, while simultaneously violating the E. coli standard. This study will help to clarify the effects of land development on the pathogen properties of stream water in the Georgia Piedmont and examine the ramifications of using fecal coliforms and E. coli as indicators of disease-causing pathogens within the region.