Microbial source tracking to identify human and ruminant sources of faecal pollution in an ephemeral F lorida river

Aims Levels and sources of faecal indicator bacteria ( FIB ) in an ephemeral F lorida river were assessed under different rainfall/flow patterns to explore the effects of rainfall on water quality. Methods and Results Quantitative PCR for sewage markers [human‐associated B acteroides HF 183 and human polyomaviruses ( HP y V s)] and PCR for ruminant faecal markers were used to explore contamination sources. E scherichia coli , faecal coliform and enterococci levels consistently exceeded recreational water quality criteria, and sediment FIB levels were about 100‐fold higher compared with water. HP y V s detections cooccurred with HF 183, which was frequently detected near septic systems. Ruminant markers were detected only in livestock‐grazing areas. Significantly greater faecal coliform and E . coli concentrations were observed under no‐flow conditions and the levels of faecal coliforms in water column and sediments were negatively correlated with duration since last rain event. Conclusions Septic systems and cattle grazing in this watershed contributed to the formation of FIB reservoirs in sediments, which were persistent following prolonged rainfall. Significance and Impact of the Study Ephemeral water bodies that flow only under the direct influence of recent rainfall are rarely studied. FIB levels in the N ew R iver in F lorida were greater during dry weather than wet weather, which contrasts with most observations and may be attributed to bacterial reservoirs formed in still pool, sediments and water‐saturated soils in this subtropical environment.