NEHA December 2022 Journal of Environmental Health

8 Volume 85 • Number 5 A D VANC EME N T O F T H E SCIENCE Introduction The presence of fecal matter is a cause of water body impairment in the U.S. and globally. Fecal contamination poses public health risks associated with pathogens (Cabral, 2010; Wade et al., 2010) as well as other concerns such as excess nutrients leading to eutrophication (Pinckney et al., 2001). Water bodies often are declared closed when impairment is suspected, causing loss of access by both recreational and commercial users, thereby resulting in economic damages in the community (Rabinovici et al., 2004). While proxy measures associated with impairment (e.g., rainfall amount) often are used for such closures, a common means to trigger the closure of water bodies is the detection of fecal indicator bacteria (FIB) such as E. coli or enterococci that are found primarily or exclusively in feces, which can be easily quantified. Although monitoring for FIB has been used to assess water quality for decades, there are many limitations of this method, including a poor correlation with health risks (Colford et al., 2007) and a lack of information regarding the source of the contamination. While point sources of fecal contamination have been addressed largely through improved infrastructure, sites that continue having elevated bacterial counts (possibly due to fecal contamination) experience contribution from numerous and diŠcult-to-identify nonpoint sources of fecal matter or bacteria. An important first step in the process of source identification is the ability to identify the species contributing to elevated FIB counts. Source identification is particularly relevant at the watershed scale where numerous sources likely contribute to contamination. Without being able to quickly identify fecal contamination sources via testing, water quality managers rely on time-consuming and costly surveys that are often unsuccessful at identifying the sources. Additionally, unknown sources limit the ability for mitigation and risk assessment in watersheds that experience contamination. Our project design was an attempt to remove proxy measures used to make public health decisions and use DNA source tracking to determine the sources of bacteria as a means of assessing risk levels. To address the limitations of traditional FIB monitoring, a microbial source tracking toolbox has been developed that includes a range of methodologies (Scott et al., 2002). One promising option within this toolbox is the amplification of selected DNA fragments via polymerase chain reaction (PCR). PCR can be used to amplify a variety of markers including those found in fecal pathogens (Harwood et al., 2014; Korajkic et al., 2018) or the same FIB traditionally used for culture-based detection (Chern et al., 2011; Haugland et al., 2010; Kildare et al., 2007). By targeting genetic markers within the bacteria that are specific to a given host (i.e., Abs t r ac t 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 flowing 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-specific 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. Microbial Source Tracking in the Sasco Brook, Lower Farm River, and Goodwives River Watersheds of Long Island Sound Lauren Brooks, PhD Biology Department, Utah Valley University Adalgisa Caccone, PhD Department of Ecology and Evolutionary Biology, Yale University Mark Cooper, MPH, RS Westport–Weston Health District David Knauf, MPH, MS, REHS Health Department, Town of Darien Michael A. Pascucilla, MPH, REHS, DAAS East Shore District Health Department