Chemical and Pathogen 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.
U.S. Geological Survey (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.
- 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 Racking of Septic Effluents in Shallow Groundwater -- 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.