Attenuation and persistence of fecal indicator bacteria in vegetated buffer strips in Southern Illinois, USA

Enteric microbial pathogens originating from agricultural practices pose a serious threat to surface water quality and human health. A two-phase study was conducted in southern Illinois that examined the ability of various riparian buffer species to attenuate fecal coliform bacteria and Escherichia coli (E. coli) in overland flow, while also assessing E. coli persistence in associated buffer soils. Plots established with giant cane (Arundinaria gigantea (Walt.) Muhl.), Kentucky Bluegrass (Poa pratensis), Orchardgrass (Dactylis glomerata L.), and non-vegetated control buffers were subjected to artificial flooding with cattle (Bos taurus) manure-laden water. Mean bacteria concentrations in overland flow exiting all plots were significantly higher than concentrations found in the source slurry. To assess E. coli persistence in plots, overland flow was collected from a simulated rainfall event 4 days following slurry application, and from natural rainfall events 22, 46, 94, 97, and 111 days after the application. Overland flow exiting all plots (including non-vegetated controls) exhibited mean E. coli concentrations significantly higher than those found in the initial slurry applied. The observed concentrations may have been the result of overland flow characteristics and high levels of ambient fecal indicator bacteria (FIB) present with plots. The moist, shaded conditions created by plot vegetation may have produced prime habitat to harbor FIB. Vegetated buffer strips (VBS) may have been effective at attenuating FIB, however, performance may have been masked by the exceptionally high ambient FIB populations that were present in adjacent soils. The young age of the VBS (<1 year) may have also influenced their seemingly poor FIB attenuation. As the VBS age, increases in above and below ground vegetative material may act to increase VBS attenuation capabilities.