The dynamics of faecal indicator organisms in a temperate river during storm conditions

Greater incidence of storm events, which can lead to greater contamination of surface waters by human and animal faeces, are a predicted feature of climate change in parts of Europe and elsewhere. The aim of this study was to combine the use of a novel quantitative microbial source tracking (QMST) method with established water quality monitoring procedures during an intense summer storm event in a rural UK river catchment, to establish dominant sources of faecal pollution. One-litre grab samples of river water were collected every 12 h for a period of seven days from three sampling sites on the Bevern Stream (a tributary of the Sussex Ouse). All samples were tested for a range of chemophysical and bacteriological parameters, and also for phage-lysis of a human specific strain of Bacteroides spp. GB-124. Presumptive levels of Escherichia coli and intestinal enterococci were statistically significantly (p-value < 0.05) higher during the storm event, compared with dry weather conditions. Low recorded levels of phages of Bacteroides GB-124 during the storm event, compared with dry weather conditions, support the hypothesis that the predominant sources of faecal material in the river during the storm event were non-human. Using traditional faecal indicator bacteria and a QMST marker during storm events may improve human health protection protocols.