Salmonella spp. and Fecal Coliform Loads in Coastal Waters from a Point vs. Nonpoint Source of Pollution

Abstract

Abstract Coastal areas are often contaminated by the dissemination of pathogenic bacteria from terrestrial inputs. In this study, we compared fecal coliforms (FC) and Salmonella spp. loads from a coastal Mediterranean river and from the submarine outfall of a coastal wastewater treatment station. A stratified sampling strategy was used to analyze storm events. Bacterial fluxes were estimated during a 16‐mo period. Salmonella spp. loads from the river were high during storm events, and the annual loads were higher than those estimated from the coastal outfall. Bacterial loads from the river represented 3.0 × 10 16 FC yr −1 and 6.9 × 10 12 Salmonella yr −1 , with at least 95% occurring during high waterflow (21% of the year). Those from the submarine outfall represented 4.3 × 10 16 FC yr −1 and 4.7 × 10 10 Salmonella yr −1 , with a regular temporal discharge. Bacterial loads from the river were associated with small clay particles (<2 µm), which originate from different reservoirs. These particles‐sediment‐trapped bacteria accumulated in the river‐bed during the lowest water levels in the downstream part of the river and were resuspended during storm events. The quantitative relationship between both bacterial parameters vary depending on the source point of contamination. Salmonella spp. loads from the river are of great sanitary concern since high loads were recorded in summer (bathing activities) and autumn (oyster production and consumption). Our results should help water quality managers to define priorities to improve the bacterial quality of river discharges.