Chemical and Pathgogen Exposure Through Recreational Waters: Microbial Source Tracking

There are a wide range of techniques available in the emerging field of microbial source tracking (MST) to help identify non-point sources of fecal contamination. Applying these techniques to recreational waters, however, is complicated by the highly dynamic currents and hydrologic processes that transport fecal-indicator bacteria and pathogens, and the complex physical, chemical, and biological processes affecting their numbers in coastal areas.

Applying a phased approach seems practical in this complex environment. A phased approach may include (1) documenting the spatial and temporal variability of fecal contamination, (2) identifying the environmental and meteorological factors that affect indicator concentrations, (3) identifying “hot spots” of fecal contamination, and (4) applying more expensive and sophisticated MST techniques to corroborate earlier findings.

USGS scientists have the tools and capabilities to address source tracking issues in recreational waters. Although all the studies listed are not specific for beaches, many of these techniques can be used in recreational waters, especially during later phases of investigations.

Completed Projects

• Examining spatial distributions of E. coli and enviromental and water-quality factors that can affect concentrations of E. coli to identify sources of fecal contamination to a popular Lake Erie bathing beach and recreational area in northwest Ohio.
  -- Downloadable Report -- Francy, D.S., Struffolino, P., Brady, A.M.G., and Dwyer, D.F., 2005, A spatial, multivariable approach for identifying proximate sources of Escherichia coli to Maumee Bay, Lake Erie, Ohio: U.S. Geological Survey Open File Report 2005-1386, 20 p.
• Using spatial sampling and microbial source-tracking tools to understand fecal contamination at two Lake Erie beaches in northeast Ohio.
  -- Report will be available soon -- Francy, D.S., Bertke, E.E., Finnegan, D.P., Kephart, C.M., Sheets, R.A., Rhoades, J., and Stumpe, L., 2006, Use of spatial sampling and microbial source-tracking tools for understanding fecal contamination at two Lake Erie beaches, U.S. Geological Survey Scientific Investigations Report 2006-5298, 29 p.
• General source tracking . The reproducibility, accuracy, and robustness of seven library-based MST protocols were evaluated by use of known sources and a blinded challenge library. These included phenotypic methods that distinguish among growth patterns expressed by microorganisms and genotypic methods that identify patterns in the genetic material of isolates.
  -- Downloadable Abstract -- Stoeckel, D.M. and others, 2004, Comparison of seven protocols to identify fecal contamination sources using Escherichia coli, Environmental Science and Technology, v. 33, no. 22, pp. 2109-6117 (November 15, 2004 issue).
• Evaluation of the dynamics of Escherichia coli and enterococci in gull feces . The temporal variability in DNA fingerprints and biochemical profiles of fecal indicator bacteria in gull feces were studied.
  -- Downloadable Report -- Fogarty, L. R., Haack, S. K., Wolcott, M. J., and Whitman, R. L., 2003, Abundance and characteristics of the recreational water quality indicator bacteria Escherichia coli and enterococci in gull faeces: Journal of Applied Microbiology, v. 94, pp.865-878.
• Understanding how environmental factors influence source-tracking at beaches . Weather patterns, beach conditions, and hydrodynamics in a Great Lakes bay influence how fecal indicator bacteria are delivered to beaches from several sources.
  -- Downloadable Report -- Haack, S. K., Fogarty, L. R., and Wright, Christopher, 2003, Escherichia coli and enterococci at beaches in the Grand Traverse Bay, Lake Michigan: sources, characteristics and environmental pathways Environmental Science and Technology, v. 37, pp. 3275-3282.
  -- Downloadable Abstract -- Francy, D.S. and Darner, R.A., 1998, Factors affecting Escherichia coli concentrations at Lake Erie public bathing beaches: U.S. Geological Survey, Water-Resources Investigations Report 98-4241, 41 p.
• Understanding the importance of Escherichia coli in sediments and beach sands . High concentrations of Escherichia coli in sediments and beach sands may be of some concern for public health.
  -- Downloadable fact sheet -- Escherichia coli in the Swash Zone at Four Ohio Bathing Beaches.
  -- Downloadable Report -- Whitman, R.L., and Nevers, M.B., 2003, Foreshore sand as a source of Escherichia coli in nearshore water of a Lake Michigan beach, Applied and Environmental Microbiology, v. 69, no. 9, p. 5555-5562.

Current Projects

• Source tracking at recreational beaches . Investigators are identifying the spatial distribution of E. coli at two Lake Erie beaches and then applying MST techniques. These include the identification of human enteric viruses, genotyping of F-specific coliphage, and testing the antibiotic resistance of E. coli isolates.
• Modeling and source-tracking tools for understanding fecal contamination and predicting recreational water quality at Ohio beaches.
• Source tracking in streams for Total Maximum Daily Loads (TMDL) . E. coli isolates from a small stream in Nebraska are analyzed using repetitive element-PCR (specifically, BOX-PCR) to determine the originating host, whether from human, cattle, swine, or other sources. A second MST method, coliphage genotyping, is tested for corroborating evidence.
• Microbial Source Tracking in the Plum Creek Watershed, Nebraska
• Source tracking of septic effluents in shallow ground water . Investigators used a MST technique to specifically define sources of septic contaminants to ground water. The use of genomic subtyping using rep-PCR will allow implication of a single septic system as a source of fecal contamination to ground water.
• Relation of Septic-System Construction and Site Characteristics to Shallow Ground-Water Quality in Ohio
• Source tracking in a recreational bay . Investigators are determining the spatial and temporal distribution of E. coli in bed sediments and examining the relations between environmental and water-quality variables and concentrations of E. coli to help identify sources of fecal contamination to Maumee Bay in Lake Erie.
• Evaluation of Bacteroides-Prevotella and Bifidobacterium Communities for Use in Fecal Source Tracking Studies. The approach of this study is to use a community DNA fingerprinting technique, t-RFLP (terminal restriction fragment length polymorphism) to identify unique DNA fingerprints for different possible sources of fecal material (human, cattle, seagulls, etc.). Results of this study will improve our understanding of the fecal bacteria community and aide in determining the sources of fecal contamination.
• Blue Marsh Lake ( Berks County, PA.) bacteria source identification pilot project. Blue Marsh Lake provides the public with activities that include swimming, boating, fishing, water skiing, and sailing. Occasionally, fecal coliform concentrations in the lake have exceeded recreational water-quality standards. The preliminary study will focus on the distribution of fecal contamination by measuring selected bacterial concentrations in the lake itself, the perennial tributaries that flow into the lake, and sand samples from the beach at the swimming area.

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