Assessment of Nutrient and Bacteria Contributions from Watersheds with Predominantly Agricultural and Urban Land Uses in Coastal North Carolina

Excess concentrations of fecal indicator bacteria, nitrogen, and phosphorus have caused closure of shellfish growing waters, swimming advisories, eutrophication, and impairment of aquatic habitat in the Tar–Pamlico Estuary, North Carolina. Regulatory requirements to reduce nutrient and bacteria loading to the estuary were enacted more than two decades ago, but water quality problems persist. The goals of this study were to (1) assess the nutrient and bacteria concentrations and exports from Jacks Creek and Runyon Creek to the Tar–Pamlico Estuary in Coastal North Carolina, USA, and (2) recommend watershed-specific practices to reduce pollutant loadings and improve estuarine water quality. Stream water samples were collected for nutrient, bacteria, and physicochemical property (flow, pH, temperature, turbidity, and dissolved oxygen) analyses from five segments of Jacks Creek and six segments of Runyon Creek. Samples were collected between 8 and 10 times over a two-and-a-half-year period (2021–2024). Mean concentrations of total dissolved nitrogen, total dissolved phosphorus, and E. coli for Jacks Creek (1.55 mg/L, 0.10 mg/L, 502 MPN/100 mL) and Runyon Creek (1.70 mg/L, 0.07 mg/L, 262 MPN/100 mL) exceeded reference conditions or thresholds established by the US EPA (0.69 mg/L, 0.036 mg/L, 126 MPN/100 mL). Therefore, both watersheds have been contributing to the nutrient and bacteria problems of the estuary. Implementation of stormwater control measures in the urbanized Jacks Creek Watershed and agricultural best management practices in the Runyon Creek Watershed is encouraged. Some of the suggested practices have been installed, but additional remediation efforts are needed.