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Title: Characterizing relationships among fecal indicator bacteria, microbial source tracking markers, and associated waterborne pathogen occurrence in stream water and sediments in a mixed land use watershed

item BRADSHAW, J.K. - Oak Ridge Institute For Science And Education (ORISE)
item SNYDER, B.J. - Us Environmental Protection Agency (EPA)
item OLADEINDE, A - Us Environmental Protection Agency (EPA)
item SPINDLE, D - Us Environmental Protection Agency (EPA)
item Berrang, Mark
item Meinersmann, Richard - Rick
item OAKLEY, B - Former ARS Employee
item SIDLE, R.C. - University Of Sunshine Coast
item MOLINA, M - Us Environmental Protection Agency (EPA)

Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2016
Publication Date: 5/13/2016
Citation: Bradshaw, J., Snyder, B., Oladeinde, A., Spindle, D., Berrang, M.E., Meinersmann, R.J., Oakley, B., Sidle, R., Molina, M. 2016. Characterizing relationships among fecal indicator bacteria, microbial source tracking markers, and associated waterborne pathogen occurrence in stream water and sediments in a mixed land use watershed. Water Research. doi: 10.1016/j.watres.2016.05.014.

Interpretive Summary: Streams and rivers, often used for recreation, may be contaminated by bacteria associated with land use such as agriculture or waste water treatment plants adjacent to the stream. Such contamination may introduce bacteria such as fecal indicator bacteria or even human pathogens into the waterway. This survey was undertaken to examine the relationship between land use and the presence of fecal indicator bacteria, pathogenic bacteria and bacterial markers related to potential sources such as cattle in stream water and the sediment of the stream bed. Fifteen sites in the watershed of the South Fork of the Broad River (SFBR) in Northeastern Georgia, USA, were sampled for water and sediment in three seasons. Each season there were three replicate sample trips taken every other week. Sites represented agricultural, forest and waste water treatment land use. Water and sediment were cultured for fecal indicator bacteria, specific bacterial pathogens: Campylobacter, Listeria and Salmonella, Shiga toxin genes and checked for microbial source tracking markers for cow/ruminant. Campylobacter, Listeria and Salmonella were more often detected in water than in sediment. Fecal indicator bacteria were the opposite being more often detected in sediment. Detection of Shiga toxin gene was related to land use and the detection of cow/ruminant markers. Relationships between indicators and human pathogens were inconsistent; no single indicator was useful to predict the presence of all pathogens. General fecal indicator bacteria and microbial source tracking markers may be the best tools to monitor water quality in mixed land use water sheds.

Technical Abstract: Bed sediments of streams and rivers may store high concentrations of fecal indicator bacteria (FIB) and pathogens. These contaminants can be mobilized into the water column due to resuspension events, thus affecting overall water quality. Along with the contaminants, other markers such as microbial source tracking (MST) markers, developed to determine potential sources of fecal contamination, can also be resuspended from bed sediments. Land use may play an important role in the concentrations and distribution of FIB, MST markers, and the occurrence of pathogens in stream water and sediments. The primary objective of this study was to evaluate FIB, MST markers, and waterborne pathogen occurrence in water and stream bed sediments as a function of land use and examine relationships between pathogen occurrences and indicator and marker concentrations (FIB and/or MST). Synoptic sampling events were conducted during baseflow conditions downstream from agricultural (AG), forested (FORS), and waste water pollution control plant (WPCP) land uses; concentrations of FIB and MST markers were measured in water and sediments along with occurrences of the enteric pathogens Campylobacter, Listeria, and Salmonella, and the virulence gene that carries Shiga toxin, stx2. Pathogens were detected more often in water than in underlying sediments, while FIB and MST marker concentrations were higher in sediments. Shiga toxin was significantly dependent on land use; concentrations of cow and ruminant markers were selected as independent variables that could correctly classify 88 to 96% of observed Shiga toxin occurrences in water and sediment. Fecal indicator bacteria concentrations and water quality parameters were also selected as independent variables that correctly classified Shiga toxin occurrences in water and sediment (56 to 87%), and Salmonella occurrences in water (96%). Specifically, cow and ruminant MST marker concentrations were better predictors of Shiga toxin occurrence, while FIB and water quality variables (D.O., pH, and temperature) were better for predicting Salmonella. Overall relationships between pathogens and indicator variables were inconsistent and no single indicator adequately described the occurrence of all pathogens. Therefore, incorporating FIB, water quality measurements, and MST markers may be the best way to assess microbial water quality in mixed land use systems because of the inconsistent relationships between individual pathogens and FIB/MST markers.