Identify Sources of Fecal Contamination using Molecular (DNA) Approaches
Many surface waters and beaches do not meet water quality standards due to elevated levels of fecal indicator bacteria (e.g. E.coli). Microbial source tracking employing DNA based methods can aid in identifying sources of fecal pollution so that control measures can be implemented to protect our waters.
More than 30 years after the Clean Water Act, approximately 13% of US surface waters are included on the 303(d) list of impaired waters and beach closures and advisories exceeded 20,000 days in each of the past 4 years with more than 60% caused by fecal pollution. The problem continues due to the inability of traditional methods to identify fecal contamination sources so that control measures can be promptly implemented.
In a typical watershed, contamination of surface waters can stem from a myriad of potential point and non-point sources containing fecal material from:
- humans (sewer leaks, sanitary sewer overflows, septic system failures, stormwater),
- dogs and other domestic animals (stormwater, urban runoff),
- livestock (confined animal feeding operations), and
Traditionally, water quality has been assessed by cultivation-based enumeration of fecal indicator bacteria such as fecal coliforms and E. coli. Monitoring fecal indicator bacteria can identify impaired waterbodies and aid in protecting human health. However, traditional approaches have no real diagnostic power to identify the source of fecal pollution and direct corrective actions to improve water quality. Recognition of the limitations of traditional culture-dependent methods and indicator organisms has spawned an entire field of study termed microbial source tracking (MST) which employs cultivation-independent methods to not only assess water quality more accurately but also to identify the source of fecal contamination.