Quantifying the relative contributions of environmental sources to the microbial community in an urban stream under dry and wet weather conditions

Darshan Baral, Allison Speicher, Bruce Dvorak, David Admiraal, Xu Li

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Investigating sources of microbial contamination in urban streams, especially when there are no contributions from combined sewer overflows or sewage effluent discharges, can be challenging. The objectives of this study were to identify the sources of microbes in an urban stream and quantify their relative contributions to the microbial community in the stream under dry and wet weather conditions. A microbial source tracking method relying on the 16S rRNA gene was used to investigate the microbial communities in water samples of an urban stream (i.e., from 11 dry and 6 wet weather events), as well as in streambed sediment, soils, street sweepings, sanitary sewage, an upstream lake, and feces of animals and birds collected between 2013 and 2015. The results showed that the Escherichia coli levels in the stream were significantly higher in wet weather flow than in dry weather flow. The upstream lake contributed approximately 93% of the microbes in dry weather flows. Water discharged from storm drain outfalls was the biggest source of microbes in wet weather flows, with a median contribution of approximately 90% in the rising limb and peak flow and about 75% in the declining limb of storms. Furthermore, about 70 to 75% of the microbes in the storm drain outfall water came from materials washed off from the street surfaces in the watershed. Fecal samples did not appear to contribute substantially to the microbes in environmental samples. The results highlight the significance of street surfaces in contributing microbial loads to urban streams under wet weather conditions.

Original languageEnglish (US)
Article numbere00896-18
JournalApplied and environmental microbiology
Issue number15
StatePublished - Aug 1 2018


  • Dry weather condition
  • Microbial source tracking
  • Urban stream
  • Wet weather condition

ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology


Dive into the research topics of 'Quantifying the relative contributions of environmental sources to the microbial community in an urban stream under dry and wet weather conditions'. Together they form a unique fingerprint.

Cite this