Identifying Fecal Sources in a Selected Catchment Reach Using Multiple Source-Tracking Tools

• Published in: Journal of environmental quality Vol. 36; no. 3; pp. 718 - 729
• Main Authors: Vogel, J.R, Stoeckel, D.M, Lamendella, R, Zelt, R.B, Santo Domingo, J.W, Walker, S.R, Oerther, D.B
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy, Crop Science Society of America, Soil Science Society 01-05-2007; American Society of Agronomy
• Subjects: Animals; Animals, Wild; Bacteria; bacteriophages; Bacteroidaceae - genetics; Bacteroidales; Bed load; biomarkers; Cattle; Contamination; E coli; Environmental management; Environmental quality; Escherichia coli; Escherichia coli - genetics; excreta; Fecal coliforms; Feces; Feces - microbiology; Geologic Sediments; Horses; Humans; livestock; microbial detection; Microbiology; Nebraska; nonpoint source pollution; polymerase chain reaction; Prunus; Quality standards; Riparian buffers; Rivers; Ruminantia; sediment contamination; Sediment samplers; Streams; Surface water; Tracking equipment; Water analysis; Water Microbiology; Water Pollution; Water quality; Water sampling; watersheds; Wildlife; Nebraska; USA, Colorado, Plum Creek; USA, Nebraska
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2006.0246

Given known limitations of current microbial source-tracking (MST) tools, emphasis on small, simple study areas may enhance interpretations of fecal contamination sources in streams. In this study, three MST tools--Escherichia coli repetitive element polymerase chain reaction (rep-PCR), coliphage typing, and Bacteroidales 16S rDNA host-associated markers--were evaluated in a selected reach of Plum Creek in south-central Nebraska. Water-quality samples were collected from six sites. One reach was selected for MST evaluation based on observed patterns of E. coli contamination. Despite high E. coli concentrations, coliphages were detected only once among water samples, precluding their use as a MST tool in this setting. Rep-PCR classification of E. coli isolates from both water and sediment samples supported the hypothesis that cattle and wildlife were dominant sources of fecal contamination, with minor contributions by horses and humans. Conversely, neither ruminant nor human sources were detected by Bacteroidales markers in most water samples. In bed sediment, ruminant- and human-associated Bacteroidales markers were detected throughout the interval from 0 to 0.3 m, with detections independent of E. coli concentrations in the sediment. Although results by E. coli-based and Bacteroidales-based MST methods led to similar interpretations, detection of Bacteroidales markers in sediment more commonly than in water indicates that different tools to track fecal contamination (in this case, tools based on Bacteroidales DNA and E. coli isolates) may have varying relevance to the more specific goal of tracking the sources of E. coli in watersheds. This is the first report of simultaneous, toolbox approach application of a library-based and marker-based MST analyses to flowing surface water.