Cattle MST Case Studies
1. Cattle Markers Exceed Water Quality Criteria in Brandywine Creek
Water samples taken from the Brandywine Creek Basin in Delaware that exceeded the E. coli and the Enterococci recreational water-quality criteria (RWQC) more frequently contained markers of cattle feces or bovine sources, according to a study released in 2011 by the U.S. Department of the Interior and the U.S. Geological Survey in cooperation with the City of Wilmington, Delaware.
The study entitled, “Pathogenic Bacteria and Microbial-Source Tracking Markers in Brandywine Creek Basin, Pennsylvania and Delaware, 2009–10,” was intended to help in understanding the occurrence and distribution of fecal indicator bacteria (FIB), fecally derived pathogens, and potential fecal sources that contribute to microbial water-quality impairments. “Brandywine Creek drains a mixed-land-use basin that contains agricultural, urban, and suburban areas and has within it several wastewater-treatment discharges and industrial and public-supply withdrawals. The City of Wilmington, Delaware, which is in the downstream part of the basin on the main stem of Brandywine Creek, uses the stream for its main drinking-water supply.”
The City of Wilmington, which has been investing in best-management-practices (BMP) projects in the Brandywine Creek since 2005, was interested in determining the potential sources of the fecal pollution and pathogens in the basin. Researchers sampled water monthly for one year during high flow and normal flow at five routinely sampled sites within the basin as well as three additional sites located upstream of the West and East Branches. “The collected samples were analyzed for the densities of the FIB, Escherichia coli (E. coli), Enterococci, and fecal coliform bacteria. DNA extracted directly from each water sample was analyzed for the quantity of each of three types of Bacteroides microbial source tracking (MST) markers indicating general, bovine, and human fecal pollution.”
One of the study’s findings was that the E. hirae bovine fecal marker was found more frequently in the West Branch than the East Branch during high flow. Researchers believe this indicates that elevated FIB densities in the West Branch are more frequently related to bovine sources than in the East Branch. Researchers also found that water from the West Branch that was carrying FIB of bovine origin spilled over to other areas triggering positive results in those sites at certain times.
A copy of the study is available here.