Differential occurrence of Escherichia coli and human Bacteroidales at two Great Lakes beaches

Staley, Zachery R.; Vogel, Laura J.; Robinson, C. E.; Edge, Thomas A.

doi:10.1016/j.jglr.2015.03.006

Cited by 20 publications

(6 citation statements)

References 33 publications

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“…These findings suggest that E. coli in beach sand is favored under high-moisture conditions, and enterococci are favored under low-moisture conditions, irrespective of source inputs. Water samples harbored lower concentrations of E. coli and enterococci per 100 ml, compared to 100-g berm or backshore sand samples, consistent with a recent study by Staley et al (54). Although a determination of bacterial transfer dynamics between sand and water are not within the aims of this study, the high correlation of FIB between berm sand and water suggests that the sand FIB-carrying capacity is large and has the potential to seed FIB to the nearshore water.…”

Section: Discussionsupporting

confidence: 89%

Distribution and Differential Survival of Traditional and Alternative Indicators of Fecal Pollution at Freshwater Beaches

Cloutier

McLellan

2017

Appl Environ Microbiol

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Alternative indicators have been developed that can be used to identify host sources of fecal pollution, yet little is known about how their distribution and fate compare to traditional indicators. Escherichia coli and enterococci were widely distributed at the six beaches studied and were detected in almost 95% of water samples (n ϭ 422) and 100% of sand samples (n ϭ 400). Berm sand contained the largest amount of E. coli (P Ͻ 0.01), whereas levels of enterococci were highest in the backshore (P Ͻ 0.01). E. coli and enterococci were the lowest in water, using a weight-to-volume comparison. The gull-associated Catellicoccus marimammalium (Gull2) marker was found in over 80% of water samples, regardless of E. coli levels, and in 25% of sand samples. Human-associated Bacteroides (HB) and Lachnospiraceae (Lachno2) were detected in only 2.4% of water samples collected under baseflow and post-rain conditions but produced a robust signal after a combined sewage overflow, despite low E. coli concentrations. Burdens of E. coli and enterococci in water and sand were disproportionately high in relation to alternative indicators when comparing environmental samples to source material. In microcosm studies, Gull2, HB, and Lachno2 quantitative PCR (qPCR) signals were reduced twice as quickly as those from E. coli and enterococci and approximately 20% faster than signals from culturable E. coli. High concentrations of alternative indicators in source material illustrated their high sensitivity for the identification of fecal sources; however, differential survival and the potential for long-term persistence of traditional fecal indicators complicate the use of alternative indicator data to account for the levels of E. coli and enterococci in environmental samples. IMPORTANCE E. coli and enterococci are general indicators of fecal pollution and may persist in beach sand, making their use problematic for many applications. This study demonstrates that gull fecal pollution is widespread at Great Lakes beaches, whereas human and ruminant contamination is evident only after major rain events. An exploration of sand as a reservoir for indicators found that E. coli was ubiquitous, while gull host markers were detected in only 25% of samples. In situ sand beach microcosms provided decay rate constants for E. coli and enterococci relative to alternative indicators, which establish comparative benchmarks that would be helpful to distinguish recent from past pollution. Overall, alternative indicators are useful for identifying sources and assessing potentially high health risk contamination events; however, beach managers should be cautious in attempting to directly link their detection to the levels of E. coli or enterococci.KEYWORDS beaches, water quality, human-associated indicators, gull-associated indicators, qPCR F ecal contamination of recreational waters can be a serious threat to public health. Due to the vast diversity of fecal-borne human pathogens, the USEPA has recommended the use of fecal indicator bacteria (FIB),...

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Section: Discussionsupporting

confidence: 89%

Distribution and Differential Survival of Traditional and Alternative Indicators of Fecal Pollution at Freshwater Beaches

Cloutier

McLellan

2017

Appl Environ Microbiol

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“…The behavior of OM and fecal bacteria near the SWI are of considerable interest in beach aquifers as they impact nutrient cycling and recreational water quality, respectively. While it is well established that fecal bacteria accumulate at high concentrations in shallow sand and groundwater in the swash zone [ Whitman and Nevers , ; Solo‐Gabriele et al ., ; Staley et al ., ], improved understanding of the mechanisms by which the bacteria are transferred to the adjacent surface water is needed to better predict the fate of bacteria in beach environments and thus to improve recreational water quality forecasting models.…”

Section: Introductionmentioning

confidence: 99%

Influence of instantaneous and time‐averaged groundwater flows induced by waves on the fate of contaminants in a beach aquifer

Malott

O'Carroll

Robinson

2017

Water Resources Research

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Wave‐induced water exchange and groundwater flows in beach aquifers impact the fate of contaminants including nutrients, fecal bacteria, and nonaqueous phase liquids (NAPLs). Waves induce high‐frequency fluxes in shallow beach sediments. In addition, the phase‐averaged effect of waves (wave setup) drives deeper flow recirculations through a beach aquifer. Field data of shallow instantaneous and time‐averaged vertical head gradients (fluxes) are first compared with deeper time‐averaged fluxes over a period of varying wave conditions. The time‐averaged fluxes are equivalent to that which would be simulated assuming a phase‐averaged water surface (i.e., wave setup). Based on this comparison, the need to simulate phase‐resolved wave motion versus the simplified phase‐averaged water surface in predicting contaminant fate is evaluated. While high‐frequency fluxes cause large surface water volumes to filter through beach sediments, the exchanging water has a short residence time (<1–70 s). The time‐averaged flow behavior captures exchanging water with longer residence time (hours to months) and deeper flow paths. Therefore, consideration of the time‐averaged behavior may be sufficient for evaluating dissolved reactive constituents. In contrast, calculations indicate that instantaneous fluxes may need to be considered in evaluating colloidal contaminants (e.g., particulate organic matter and fecal bacteria) as sediment interactions affect their transport and residence time. Finally, multiphase simulations illustrate the differential effect of considering instantaneous versus time‐averaged fluxes on the downward migration of NAPL in beach sediments. This study provides an important foundation for future field and modeling efforts focused on understanding and predicting contaminant transport in wave‐influenced beaches.

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“…This may alter the pH and redox gradients, stimulate reactive processes (e.g., reductive dissolution of metal hydroxides and release of adsorbed constituents) [ Lee et al ., ], and in turn affect the fate of contaminants discharging through the aquifer. Varying geochemical conditions may also influence the survival of microbial bacteria (e.g., E. coli and enterococci ) that are known to accumulate in shallow groundwater and sand near the shoreline [ Alm et al ., ; Vogel et al ., ; Whitman et al ., ; Staley et al ., ]. While temporal variations of pH and redox conditions in the shallow nearshore aquifer have been observed previously in response to spring‐neap tidal fluctuations [ Robinson et al ., ], the extent to which wave events affect these conditions remains unclear.…”

Section: Introductionmentioning

confidence: 78%

Dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event

Malott

O'Carroll

Robinson

2016

Water Resources Research

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Dynamic coastal forcing influences the transport of pollutants in nearshore aquifers and their ultimate flux to coastal waters. In this study, field data are presented that show, for the first time, the influence of a period of intensified wave conditions (wave event) on nearshore groundwater flows and geochemistry in a sandy beach. Field measurements at a freshwater beach allow wave effects to be quantified without other complex forcing that are present along marine shorelines (e.g., tides). Pressure transducer data obtained over an isolated wave event reveal the development of transient groundwater flow recirculations. The groundwater flows were simulated in FEFLOW using a phase‐averaged wave setup approach to represent waves acting on the sediment‐water interface. Comparison of measured and simulated data indicates that consideration of wave setup alone is able to adequately capture wave‐induced perturbations in groundwater flows. While prior studies have shown sharp pH and redox spatial zonations in nearshore aquifers, this study reveals rapid temporal variations in conductivity, pH, and redox (ORP) in shallow sediments (up to 0.5 m depth) in response to varying wave conditions. Comparison of head gradients with calculated conductivity and pH mixing ratios indicates the controlling effect of the wave‐induced water exchange and flows in driving the observed geochemical dynamics. While we are not able to conclusively determine the extent to which temporal variations are caused by conservative mixing versus reactive processes, the pH and ORP variations observed will have significant implications for the fate of reactive pollutants discharging through sandy nearshore aquifers.

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Differential occurrence of Escherichia coli and human Bacteroidales at two Great Lakes beaches

Cited by 20 publications

References 33 publications

Distribution and Differential Survival of Traditional and Alternative Indicators of Fecal Pollution at Freshwater Beaches

Distribution and Differential Survival of Traditional and Alternative Indicators of Fecal Pollution at Freshwater Beaches

Influence of instantaneous and time‐averaged groundwater flows induced by waves on the fate of contaminants in a beach aquifer

Dynamic groundwater flows and geochemistry in a sandy nearshore aquifer over a wave event

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