Microbial Source Tracking in the Sasco Brook, Lower Farm River, and Goodwives River Watersheds of Long Island Sound

Shortcomings in traditional methods for understanding sources of bacteriological contamination limit the ability of public health o cials to adequately protect public health and mitigate pollution sources. This study used polymerase chain reaction (PCR) as a tool for microbial source tracking to attempt to identify host species contributing bacteria to three watersheds fl owing into Long Island Sound. Samples were collected once a month near the mouth of each watershed and analyzed for other E. coli (a traditional fecal indicator) and genetic markers for members of the phylum Bacteroidetes. Genetic markers included host-specifi c markers that can be used to identify sources of contamination such as humans, domestic animals, and wildlife. Despite observing elevated E. coli levels in all three watersheds, we could not make a conclusive determination of actual sources using the available tools. Additionally, as there was disagreement between the E. coli levels and the presence of the general Bacteroidetes marker, it is important to evaluate the accuracy of this indicator with respect to recent fecal contamination and human health risks. Limitations posed by using indicator organisms, such as enterococci, illustrate the need to develop other methodologies for assessing actual sources of bacterial contamination.