Cattle access to small streams increases concentrations of Escherichia coli in bed sediments.

Small streams dominate the hydrological network within Europe. In many regions, these waterbodies drain large areas of agricultural land and are vulnerable to pressures linked to livestock management, which can include direct livestock access. This study investigated the impacts of cattle access to watercourses on the contamination of streambed sediment with Escherichia coli (E. coli) in five agricultural catchments. Sediments were collected at cattle access sites and at areas upstream with no cattle access, in two time points in the livestock management cycle (mid-grazing and post-grazing season). Relatively high E. coli concentrations of 103 to 104 CFU g dry wt−1 were found at sites with no access in mid-grazing season. However, concentrations were significantly higher at sites with cattle access. E. coli was present, but in generally lower concentrations, in the post-grazing season. Additionally, the study found a significant negative relationship between the quality of the general riparian environment and E. coli bed sediment concentrations at the cattle access sites in the mid-grazing season, and a significant positive relationship between E. coli concentrations and estimated cattle density locally in post-grazing season. These findings indicate that allowing livestock access to watercourses can have implications for both water quality and human health. [ABSTRACT FROM AUTHOR]