title: Efficacy of Bacteroides measurements for reducing the statistical uncertainty associated with hydrologic flow and fecal loads in a mixed use watershed.
abstract: This paper presents an analysis of the occurrence and uncertainty of source-specific Bacteroides and Escherichia coli in a stream in a mixed land-use watershed with human, cattle, and wildlife fecal inputs located in a karstic geologic region during baseflow conditions. The objectives of the study were to evaluate the occurrence, hydrologic significance, and source of fecal mass in the stream using assays for total Bacteroides (AllBac) and bovine-specific Bacteroides (BoBac), and then to compare these measurements with E. coli densities and loads. Samples were collected during baseflow conditions over several months at seven different main channel sites in the Stock Creek watershed, a 49.3 km2 basin located in Knoxville, TN (USA). We determined instantaneous loads for total fecal loads, bovine fecal loads, and E. coli from measured flow rates and the representative Bacteroides fecal masses and/or E. coli densities. The study indicated a strong correlation between total fecal load (kg d(-1)), bovine fecal load (kg d(-1)), E. coli load rate (CFU d(-1)), 7-d antecedent precipitation, and turbidity. The various datasets were used to establish parameter correlations and spatial dependencies throughout the watershed. The data analysis demonstrated two prevalent patterns throughout the watershed: (i) a runoff-dominated transport and occurrence; and (ii) potential groundwater-dominated transport and occurrence.
authors.affiliation: Institute for a Secure and Sustainable Environment, The University of Tennessee, 311 Conference Center Building, Knoxville, TN 37996-4134, USA. rgentry@utk.edu
authors.forename: Randall W
authors.initials: RW
authors.lastname: Gentry
authors.forename: Alice C
authors.initials: AC
authors.lastname: Layton
authors.forename: Larry D
authors.initials: LD
authors.lastname: McKay
authors.forename: John F
authors.initials: JF
authors.lastname: McCarthy
authors.forename: Dan E
authors.initials: DE
authors.lastname: Williams
authors.forename: Shesh R
authors.initials: SR
authors.lastname: Koirala
authors.forename: Gary S
authors.initials: GS
authors.lastname: Sayler
mesh_terms: D000818:Animals; D001439:Bacteroides / Q000302:isolation & purification*; D002417:Cattle; D003627:Data Interpretation, Statistical; D004926:Escherichia coli / Q000302:isolation & purification; D005243:Feces / Q000382:microbiology*; D005618:Fresh Water / Q000382:microbiology*; D006801:Humans; D014871:Water Microbiology; D014872:Water Movements; D014881:Water Supply