Tracing nutrient pollution from industrialized animal production in a large coastal watershed

One of the highest concentrations of swine and poultry concentrated animal feeding operations (CAFOs) in North America is located on the Coastal Plain of North Carolina, in which the Cape Fear River basin is located. The CAFOs produce vast amounts of manure causing loading of nutrients and other pollutants to receiving waters. With the Cape Fear River basin vulnerable to nutrient pollution, as are many other watersheds with CAFOs, δ13C and δ15N stable isotopic signatures were identified from water samples collected within the Northeast Cape Fear, Black, and lower Cape Fear River watersheds to trace nutrient sources and their distribution downstream. The spatial and temporal variability of nutrients and isotopic signatures were also identified to understand water quality impacts of animal waste spraying season and proximity to CAFOs. Our results showed that significantly enriched δ15N signatures characterized sites in close proximity to CAFOs as well as point-source wastewater discharge areas, while the opposite was true for an unimpacted control stream and two estuarine sites. Additionally, the impacted sites yielded significantly (p