Spatial and temporal dynamics of bacterial contamination in South France coastal rivers: focus on in-stream processes during low flows and floods

Abstract

Abstract:Faecal indicator bacteria (thermotolerant coliform and faecal streptococci) were enumerated in a Mediterranean coastal river to evaluate bacterial contamination levels in relation to hydrological conditions, to estimate delivery of bacterial loads to transitional and coastal waters (Thau lagoon) and to identify bacterial sources of pollution and their contribution to the bacterial flow. Results showed that (1) in low flow conditions, mean bacterial concentrations were higher than EU guidelines for bathing waters; (2) floods had higher concentrations of indicator bacteria than low flows; (3) low flow conditions represented a negligible proportion of bacterial loads compared with high flow and flood periods; (4) during medium and low flow conditions, bacteria were stored in riverbed fine sediments forming in-stream stores that may be flushed during floods; (5) the first flush effect was highlighted during an early autumn flood as was the role of in-stream stores during the course of the flood; and (6) point sources that continuously feed the river are contributing to the pool of bacteria accumulated in the riverbed sediment.

Quantifying the impact of socioeconomic development and climate change on Escherichia coli concentrations in the Pakistani Kabul River

“…The observed positive correlation with water temperature does, therefore, not mean that increased temperature leads to the increased E. coli concentrations through bacterial growth. Positive correlation of the E. coli concentration with average water and surface air temperature was in line with other studies (Chu et al, 2013;Medema et al, 1997;Wang and Doyle, 1998). Several authors also provide the coinciding high temperature, precipitation and discharge as main reason for the positive correlation (Koirala et al, 2008;Schilling et al, 2009b) while others link it to bacterial growth (Byappanahalli et al, 2003;Hong et al, 2010;Tiefenthaler et al, 2009).…”

Occurrence and ecological determinants of the contamination of floodplain wetlands with Klebsiella pneumoniae and pathogenic or antibiotic-resistant Escherichia coli.

“…Some authors have observed the spread of contamination in rivers (Chu et al . 2014), and others have proposed models of bacterial mobility in streams (Niu and Phanikumar 2015). Thus, freshwater ecosystems, particularly rivers, are suspected to play an important role in the dispersion of human-associated bacteria into the environment and to serve as reservoirs that can potentially lead to human contamination.…”

Climate and Land Use Influences on Bacteria Levels in Stormwater

“…Non-point urban and agricultural land use zones have significant impacts on water quality and produce a large number of fecal bacteria conveyed to water bodies [13,14]. As well, climatic variables like precipitation and wet seasons in a region are suggested to have a positive correlation with the concentration of fecal bacteria in the surface waters [15][16][17].…”