Citation:

Snyder, B., M. Molina, O. Georgacopoulos, R. Sowah, AND Mike Cyterski. Seasonality of Fecal Indicator Bacteria, Microbial Source Tracking Markers, and Pathogen Occurrence in an Urbanized Stream. ASLO 2019 Aquatic Sciences Meeting, San Juan, PR, February 23 - March 04, 2019.

Impact/Purpose:

This study takes place within the Proctor Creek watershed in downtown Atlanta, Georgia, which is highly impacted by anthropogenic activities such as sewer overflows and failing infrastructure. The stream is on the EPAs 303 (d) list for impaired waters for exceeding fecal coliform standards. Since the streams use is designated for recreational activities such as fishing, a possible public health hazard exists, however, no studies have been done to ascertain if the sources are specifically human in origin. Bi-weekly grab samples were collected from 12 sites throughout the watershed and analyzed for E. coli, the MST markers HF183MGB (human) and DG3 (dog), Salmonella, Stx-2, and water chemistry parameters. Results show that the watershed is highly impacted by human fecal contamination and it is persistent and widespread throughout. Sources of human contamination are particularly high in the watershed headwaters. Dog fecal contamination was present only intermittently and, when present, in very low concentrations. Salmonella was also widespread throughout the watershed; however, data suggests that it is not originating from humans. Information from this study can be used by local and federal agencies to implement more efficient Best Management Practices (BMP) within a watershed.

Description:

Urbanized stream water quality can be impacted by many sources; anthropogenic factors, land use, or seasonality. Fecal indicator bacteria (FIB) and microbial source tracking (MST) markers are common tools used to assess changes in water quality due to these effects. The goal of this research is to determine if seasonality based on wet and dry periods influence concentration of FIB, MST markers, or pathogen occurrence within a heavily urbanized watershed. The Proctor Creek watershed has headwaters that originate in downtown Atlanta, Georgia, U.S.A. and is listed on the US Environmental Protection Agency’s (EPA) 303(d) list of impaired waters due to exceeding fecal coliform standards. Six mainstem and six tributary sites were selected throughout the watershed where grab water samples were collected on a biweekly basis for approximately two years. Samples were analyzed for E. coli by culture and molecular detection assays, a human-associated Bacteroides (HF183MGB), a dog-associated marker (DG3), Salmonella sp., and the Shiga-toxin gene Stx2, in addition to various water chemistry parameters. Generally, wet periods displayed higher concentrations of FIB and MST markers than during the dry, while Salmonella and Stx2 had similar frequencies between seasons. The watershed pourpoint site was statistically higher during the wet season for all molecular markers, except for DG3. Impervious surface was a strong predictor of MST markers when using a gradient boosting machine model. These data suggest that seasonality may be used to predict human influences in an urban watershed.

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