Transport Of Fecal Bacteria Research Articles

Short-Term Contribution of Conservation Practice Implementation to Water Quality Impairments in Small Streams

Voluntary conservation practice adoption is a key strategy to reduce the transport of non-point source pollutants from agricultural lands to downstream ecosystems. This study assessed the short-term (1 year) efficacy of conservation practices to reduce non-point source sediment, nutrient, and fecal indicator bacteria (FIB) transport from working agricultural lands on the Mississippi State University campus, Mississippi State, MS, USA. Water quality was monitored at three treatment sites downstream of the critical resource areas, two of which had paired reference locations. All five sites were monitored for one year pre- and post-conservation practice implementation. Downstream treatment sites generally had higher nutrient and sediment concentrations than upstream reference sites. The results confirmed that the total nitrogen (TN) concentration was reduced post implementation at only the treatment site with the smallest catchment area (p < 0.01). Water quality impairments from FIB were observed across all sites, while treatment locations with livestock presence were found to have significantly elevated staphylococci and E. coli levels following the conservation practice implementation during the winter period. The results of this study showed minimal improvements to TN transport, and in some cases declines in water quality evidenced by increases in FIB, one year after conservation practice implementation. The implementation of conservation practices did not improve the overall water quality to reference levels in the short-term, despite anticipated long-term benefits.

Transport and Retention of Fecal Indicator Bacteria in Unsaturated Porous Media: Effect of Transient Water Flow.

For production of clean drinking water, the processes governing bacterial remobilization in the unsaturated zone at transient water flow are critical. Although managed aquifer recharge is an effective way to dispose of pathogens, there are concerns about recontamination after heavy precipitation. To better understand how bacteria that were initially retained in porous media can be released to groundwater due to transient water content, transport experiments and modeling for Escherichia coli and Enterococcus moraviensis were conducted at the soil column scale. After inoculating dune sand columns with a bacteria suspension for 4 h, three rainfall events were performed at 24-h intervals. The effluent from sand columns was collected to analyze bacteria breakthrough curves (BTCs). After the rainfall experiments, the bacteria distribution in the sand column was determined. The collected BTCs and profile retentions were modeled with HYDRUS-1D, using different model concepts, including one-site kinetic attachment/detachment (M1), Langmuirian (M2), Langmuirian and blocking (M3), and two-site attachment/detachment (M4). After inoculation, almost 99% of the bacteria remained in the soil. The M1 and M2 bacteria models had a high agreement between observed and modeled concentrations, and attachment and detachment were two significant mechanisms for regulating bacteria movement in a porous medium with fluctuations in water flow. At the end of the experiment, the majority of bacteria were still found within the depth range of 5 cm to 15 cm. Our experiments show that E. coli is more mobile in sandy soils than E. moraviensis. The results of this study also suggest that the unsaturated zone is an important barrier between microbial contamination at the soil surface and groundwater. Follow-up studies are needed to completely understand the variables that regulate bacteria remobilization in the unsaturated zone of dune sands. IMPORTANCE At managed artificial recharge sites in the Netherlands, recontamination of infiltrated water with fecal indicator bacteria has been observed. The results of this study suggest that the unsaturated zone is an important barrier between microbial contamination at the soil surface and groundwater. Bacteria that accumulate in the unsaturated zone, on the other hand, can multiply to such an extent that they can be released into the saturated zone when saturation increases due to major rain events or a rise in groundwater level.

Assessment of Spatio-Temporal Variability of Faecal Pollution along Coastal Waters during and after Rainfall Events

More than 80% of wastewaters are discharged into rivers or seas, with a negative impact on water quality along the coast due to the presence of potential pathogens of faecal origin. Escherichia coli and enterococci are important indicators to assess, monitor, and predict microbial water quality in natural ecosystems. During rainfall events, the amount of wastewater delivered to rivers and coastal systems is increased dramatically. This study implements measures capable of monitoring the pathways of wastewater discharge to rivers and the transport of faecal bacteria to the coastal area during and following extreme rainfall events. Spatio-temporal variability of faecal microorganisms and their relationship with environmental variables and sewage outflow in an area located in the western Adriatic coast (Fano, Italy) was monitored. The daily monitoring during the rainy events was carried out for two summer seasons, for a total of five sampling periods. These results highlight that faecal microbial contaminations were related to rainy events with a high flow of wastewater, with recovery times for the microbiological indicators varying between 24 and 72 h and influenced by a dynamic dispersion. The positive correlation between ammonium and faecal bacteria at the Arzilla River and the consequences in seawater can provide a theoretical basis for controlling ammonium levels in rivers as a proxy to monitor the potential risk of bathing waters pathogen pollution.

Sediment and fecal indicator bacteria loading in a mixed land use watershed: Contributions from suspended sediment and bedload transport

Overland transport of fecal bacteria in water and their resuspension from bed sediments are important transport mechanisms that help explain the transport of enteric pathogens in watersheds. In this study, multiyear monitoring along with regression relationships between sediment and fecal indicator bacteria (FIB) were used to investigate annual loading in the South Fork Broad River watershed, located in northeastern Georgia, USA. Suspended transport was the dominant transport mechanism contributing to in-stream total annual loads for sediment (81.4-98.1%) and FIB(>98%). Annual bedload transport of FIB was small and Escherichia coli (up to 1.8%) contributed more to annual bedload FIB than enterococci (≤0.03%). Bedload contributions of FIB increased with the duration of critical discharge exceedance, indicating a prolonged risk of exposure to enteric pathogens during extended periods of high flows, which is important during major storm events. The risk of exposure to enteric pathogens through pathways such as recreational use and drinking water treatment could be much greater because fecal bacteria are released from sediment during higher flows and dominantly transported in suspension when bedload are not actively moving. Therefore, the combined contribution of fecal bacteria from overland and bedload-associated transport should be considered in risk assessments. Discharge, bedload, and FIB data collected over 2 yr in this study can supplement future hydrologic modeling and microbial risk assessment modeling efforts.

Utilization of multiple microbial tools to evaluate efficacy of restoration strategies to improve recreational water quality at a Lake Michigan Beach (Racine, WI)

Hydro-meteorological conditions facilitate transport of fecal indicator bacteria (FIB) to the nearshore environment, affecting recreational water quality. North Beach (Racine, Wisconsin, United States), is an exemplar public beach site along Lake Michigan, where precipitation-mediated surface runoff, wave encroachment, stormwater and tributary outflow were demonstrated to contribute to beach advisories. Multiple restoration actions, including installation of a stormwater retention wetland, were successfully deployed to improve recreational water quality. Implementation of molecular methods (e.g. human microbial source tracking markers and Escherichia coli (E. coli) qPCR) assisted in identifying potential pollution sources and improving public health response time. However, periodic water quality failures still occur. As local beach managers reassess restoration measures in response to climatic changes, use of expanded microbial methods (including bacterial community profiling) may contribute to a better understanding of these dynamic environments. In this 2-year study (2015 and 2019), nearshore/offshore Lake Michigan, stormwater, and tributary samples were collected to determine if, 1) the constructed wetland (~50 m from the shoreline) continued to provide stormwater separation/retention and 2) mixing between onshore sources, Root River and Lake Michigan, was increasing due to rising precipitation/lake levels. Monthly rainfall totals were 1.5× higher in 2019 than 2015, coinciding with a 0.63 m lake-level rise. The prevalence of more intense, onshore winds also increased, facilitating interaction between potential reservoirs of FIB with nearshore water through wind driven waves and lake intrusion, e.g. beach sands and the adjacent Root River. While a strong relationship existed between wet weather wetland and North Beach nearshore E. coli concentrations (all sites), bacterial communities were strikingly different. Conversely, bacterial community overlap existed between the Root River mouth and nearshore/offshore sites. These results suggest the constructed wetland can accommodate the climate-related changes observed in this study. Future restoration activities could be directed towards upstream tributary sources in order to minimize microbial contaminants entering Lake Michigan.

Evaluation of the soil and water assessment tool (SWAT) for simulating E. coli concentrations at the watershed-scale

Water quality management at the watershed level requires a framework to identify sources, apportion water quality risks and develop mitigation strategies to reduce health risks. Watershed-scale models have been used as a support tool to understand the sources, fate and transport of fecal bacteria and pathogens in the environment. The Soil and Water Assessment Tool (SWAT) model was applied in this study to understand the sources and drivers of microbial water quality in the Clouds Creek watershed in Georgia, USA. A criterion to evaluate the performance of the SWAT bacterial model was also developed in this study using the Nash-Sutcliffe Efficiency (NSE) performance measure. The SWAT model was successfully calibrated and validated for flow with Nash-Sutcliffe Efficiency (NSE) of 0.81 and 0.55, respectively. Escherichia coli (E. coli) predictions were good with NSE of 0.32 and 0.34 for the calibration and validation timeframes, respectively. Based on the criteria developed in this study, SWAT bacterial model for E. coli and fecal coliform can be judged as “satisfactory” when NSE > 0.20. The contribution of sources followed this order: in-stream cattle manure deposition > cattle manure application > poultry manure application > septic systems > wildlife manure, suggesting that a reduction in livestock access to streams would be the most effective approach to reduce fecal bacterial loads in this watershed and others impacted by fecal contamination. Finally, our results suggest that the SWAT model is capable of simulating E. coli dynamics in the Clouds Creek watershed and can provide insights into source impacts for risk management.

Sensitivity of fecal coliform bacteria transport to climate change in an agricultural watershed

Abstract Climate change is expected to have impacts on our surface water resources, especially on the deterioration of surface water quality. The objectives of this study were to develop a calibrated and validated watershed model for daily streamflow and daily fecal coliform bacteria (FCB) concentrations using the Soil and Water Assessment Tool (SWAT) for the Big Sunflower River Watershed (BSRW) and to assess the sensitivity of FCB concentrations to changes in precipitation, temperature, and CO2 concentrations. The model demonstrated reasonable performances in simulating daily stream flow (R2 = 0.64–0.77, NSE = 0.57–0.75) and FCB concentrations (R2 = 0.56–0.60, NSE = 0.23–0.40) as compared to the previous literature. The one-at-a-time sensitivity analyses showed that average FCB concentrations were sensitive to changes in rainfall, temperature, and CO2 concentrations. Increased rainfall caused greater wash-off of FCB colonies from soil surfaces, while increased temperatures caused a decrease in surface water bacteria concentrations due to increased bacteria die-off rates. The CO2 concentration parameter was determined as the least sensitive parameter in this study.

Evaluating the influence of climate change on the fate and transport of fecal coliform bacteria using the modified SWAT model

Fecal coliform bacteria (FCB) contamination of natural waters is a serious public health issue. Therefore, understanding and anticipating the fate and transport of FCB are important for reducing the risk of contracting diseases. The objective of this study was to analyze the impacts of climate change on the fate and transport of FCB. We modified both the soil and the in-stream bacteria modules in the soil and water assessment tool (SWAT) model and verified the prediction accuracy of seasonal variability of FCB loads using observations. Forty bias-correcting GCM-RCM projections were applied in the modified SWAT model to examine various future climate conditions at the end of this century (2076–2100). Lastly, we also compared the variability of FCB loads under current and future weather conditions using multi-model ensemble simulations (MMES). The modified SWAT model yielded a satisfactory performance with regard to the seasonal variability of FCB amounts in the soil and FCB loading to water bodies. The modified SWAT model presented substantial proliferation of FCB in the soil (30.1%–147.5%) due to an increase in temperature (25.1%). Also, increase in precipitation (53.3%) led to an increase in FCB loads (96.0%–115.5%) from the soil to water body. In the in-stream environment, resuspension from the stream bed was the dominant process affecting the amount of FCB in stream. Therefore, the final FCB loads increased by 71.2% because of the growing peak channel velocity and volume of water used due to an increase in precipitation. Based on the results of MMES, we concluded that the level of FCB would increase simultaneously in the soil as well as in stream by the end of this century. This study will aid in understanding the future variability of FCB loads as well as in preparing an effective management plan for FCB levels in natural waters.

Modeling the Impact of Land Use Change on Basin‐scale Transfer of Fecal Indicator Bacteria: SWAT Model Performance

Land use change from annual crops to commercial tree plantations can modify flow and transport processes at the watershed scale, including the fate and transport of fecal indicator bacteria (FIB), such as . The Soil and Water Assessment Tool (SWAT) is a useful means for integrating watershed characteristics and simulating water and contaminants. The objective of this study was to provide a comprehensive assessment of the impact of land use change on microbial transfer from soils to streams using the SWAT model. This study was conducted for the Houay Pano watershed located in northern Lao People's Democratic Republic. Under the observed weather conditions, the SWAT model predicted a decrease from 2011 to 2012 and an increase from 2012 to 2013 in surface runoff, suspended solids, and transferred from the soil surface to streams. The amount of precipitation was important in simulating surface runoff, and it subsequently affected the fate and transport of suspended solids and bacteria. In simulations of identical weather conditions and different land uses, fate and transport was more sensitive to the initial number of than to its drivers (i.e., surface runoff and suspended solids), and leaf area index was a significant factor influencing the determination of the initial number of on the soil surface. On the basis of these findings, this study identifies several limitations of the SWAT fertilizer and bacteria modules and suggests measures to improve our understanding of the impacts of land use change on FIB in tropical watersheds.

Simulation of the fate of faecal bacteria in estuarine and coastal waters based on a fractionated sediment transport model

A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.

Transport and attenuation of Salmonella enterica, fecal indicator bacteria and a poultry litter marker gene are correlated in soil columns

Millions of tons of fecal-contaminated poultry litter are applied to U.S. agricultural fields annually. Precipitation and irrigation facilitate transport of fecal-derived pathogens and fecal indicator bacteria (FIB) to groundwater. The goal of this study was to compare transport of pathogens, FIB, and a microbial source tracking marker gene for poultry litter (LA35) in a simulated soil-to-groundwater system. Nine laboratory soil columns containing four different soil types were used to evaluate microbial transport to groundwater via infiltration. Quantitative polymerase chain reaction was used to monitor Salmonella enterica Typhimurium, Escherichia coli, Enterococcus spp., Brevibacterium sp. LA35 and Bacteroidales leached from soil columns inoculated with poultry litter. S. enterica was correlated with LA35 poultry litter marker gene and FIB concentrations in column soils containing organic matter, but not in acid washed sands. In contrast, S. enterica was found to correlate with LA35 and FIB in the leachate from columns containing sand, but not with leachate from organic soil columns. The majority of recovered DNA was found in leachate of predominately sandy soil columns, and in the soil of loamy columns. At least 90% of the DNA retained in soils for each microbial target was found in the top 3cm of the column. These studies suggest that poultry litter associated pathogens and FIB are rapidly released from litter, but are influenced by complex attenuation mechanisms during infiltration, including soil type. This study advances our understanding of the potential for subsurface transport of poultry litter associated pathogens and FIB, and support the use of the LA35 marker gene for evaluating poultry litter impacts on groundwater.

Effect of Low Energy Waves on the Accumulation and Transport of Fecal Indicator Bacteria in Sand and Pore Water at Freshwater Beaches

Elevated fecal indicator bacteria (FIB) in beach sand and pore water represent an important nonpoint source of contamination to surface waters. This study examines the physical processes governing the accumulation and distribution of FIB in a beach aquifer. Field data indicate E. coli and enterococci can be transported 1 and 2 m, respectively, below the water table. Data were used to calibrate a numerical model whereby FIB are delivered to a beach aquifer by wave-induced infiltration across the beach face. Simulations indicate FIB rapidly accumulate in a beach aquifer with FIB primarily associated with sand rather than freely residing in the pore water. Simulated transport of E. coli in a beach aquifer is complex and does not correlate with conservative tracer transport. Beaches with higher wave-induced infiltration rate and vertical infiltration velocity (i.e., beaches with higher beach slope and wave height, and lower terrestrial groundwater discharge) had greater E. coli accumulation and E. coli was transported deeper below the beach face. For certain beach conditions, the amount of FIB accumulated in sand over 5-6 days was found to be sufficient to trigger a beach advisory if eroded to surface water.

Integrated hydro-bacterial modelling for predicting bathing water quality

In recent years health risks associated with the non-compliance of bathing water quality have received increasing worldwide attention. However, it is particularly challenging to establish the source of any non-compliance, due to the complex nature of the source of faecal indicator organisms, and the fate and delivery processes and scarcity of field measured data in many catchments and estuaries. In the current study an integrated hydro-bacterial model, linking a catchment, 1-D model and 2-D model were integrated to simulate the adsorption-desorption processes of faecal bacteria to and from sediment particles in river, estuarine and coastal waters, respectively. The model was then validated using hydrodynamic, sediment and faecal bacteria concentration data, measured in 2012, in the Ribble river and estuary, and along the Fylde coast, UK. Particular emphasis has been placed on the mechanism of faecal bacteria transport and decay through the deposition and resuspension of suspended sediments. The results showed that by coupling the E.coli concentration with the sediment transport processes, the accuracy of the predicted E.coli levels was improved. A series of scenario runs were then carried out to investigate the impacts of different management scenarios on the E.coli concentration levels in the coastal bathing water sites around Liverpool Bay, UK. The model results show that the level of compliance with the new EU bathing water standards can be improved significantly by extending outfalls and/or reducing urban sources by typically 50%.

海水浴场粪便指标菌迁移转化模型研究进展

致病微生物可以通过饮用水、食物或直接接触感染人群和动物。随着我国经济的高速发展和人民生活水平的提高、旅游度假经济的迅速发展，滨海浴场水质越来越受到人们的关注。海水浴场环境中的微生物污染对旅游者身体健康甚至生命安全有直接影响，越来越受到人们的重视。因此，了解、掌握和有效管理水环境中的微生物污染是相关行业和管理机构所面临的重大挑战之一。随着计算机和数值模拟技术的迅速发展，计算机模型技术正越来越多地被国内外国学者、工程咨询机构和环境管理部门应用于微生物污染的研究及制定相关政策的过程中。然而，我国关于海水浴场微生物污染预测模型的相关研究工作和发达国家相比相对滞后。本文对预测和管理海水浴场污染的有效工具数学模型的研究进展及应用进行研究和总结。 Human and animals may be infected by pathogens in water and food consumption and direct body contact with contaminated waters. With the rapid development of economy and tourism industry and growth in the living standard, bathing water quality in China is getting more attention. The marine tourism industry is the new growth point of economic development in China. Microorganism contamination of coastal bathing water sites is a major threat to swimmers; therefore, coastal bathing water quality is getting more and more attention. The ability to predict fate and transport of faecal bacteria in bathing waters is quite challenging to water managers and government authorities. In recent years, the developments of computing technology and numerical modeling technique have provided valuable tools for water scientists, consulting companies and water management authorities to apply water quality models to bathing waters. However, advances of research on prediction model for micro-organism contamination in China is relatively slow compare to developed countries. Here in this study, the recent advances of physical-based faecal bacteria fate and transport model were studied.

Modeling fecal bacteria transport and retention in agricultural and urban soils under saturated and unsaturated flow conditions

Pathogenic bacteria, that enter surface water bodies and groundwater systems through unmanaged wastewater land application, pose a great risk to human health. In this study, six soil column experiments were conducted to simulate the vulnerability of agricultural and urban field soils for fecal bacteria transport and retention under saturated and unsaturated flow conditions. HYDRUS-1D kinetic attachment and kinetic attachment-detachment models were used to simulate the breakthrough curves of the experimental data by fitting model parameters. Results indicated significant differences in the retention and drainage of bacteria between saturated and unsaturated flow condition in the two studied soils. Flow under unsaturated condition retained more bacteria than the saturated flow case. The high bacteria retention in the urban soil compared to agricultural soil is ascribed not only to the dynamic attachment and sorption mechanisms but also to the greater surface area of fine particles and low flow rate. All models simulated experimental data satisfactorily under saturated flow conditions; however, under variably saturated flow, the peak concentrations were overestimated by the attachment-detachment model and underestimated by the attachment model with blocking. The good match between observed data and simulated concentrations by the attachment model which was supported by the Akaike information criterion (AIC) for model selection indicates that the first-order attachment coefficient was sufficient to represent the quantitative and temporal distribution of bacteria in the soil column. On the other hand, the total mass balance of the drained and retained bacteria in all transport experiments was in the range of values commonly found in the literature. Regardless of flow conditions and soil texture, most of the bacteria were retained in the top 12 cm of the soil column. The approaches and the models used in this study have proven to be a good tool for simulating fecal bacteria transport under a variety of initial and boundary flow conditions, hence providing a better understanding of the transport mechanism of bacteria as well as soil removal efficiency.

Role of Environmental Forcings on Fecal Contamination Behavior in a Small Intermittent Coastal Stream: Case Study of the Aljezur Coastal Stream, Portugal

AbstractThe role of environmental forcings on the fecal contamination dynamics in small coastal streams was investigated, using the Aljezur coastal stream (Portugal) as a test case. An integrated modeling approach, combining hydrological and coupled hydrodynamic-fecal indicator bacteria models, was applied to selected scenarios of relevant forcings, on the basis of previously calibrated and validated model applications. The forcings investigated included: tides, winds, waves, atmospheric pressure, bathymetry, river flow, and upstream fecal bacteria concentrations; this study targeted the characterization of the relative importance of these factors on the fecal contamination dynamics, to enhance our understanding of small coastal streams water quality dynamics. Results highlight distinct patterns for dry and wet periods. Fecal bacteria transport is mainly forced by tidal propagation, in dry periods; and by freshwater flows, during wet periods. The analysis reveals a complex hydraulic and water quality dyna...

Modelling the fate and transport of faecal bacteria in estuarine and coastal waters

This paper details a numerical model developed to predict the fate and transport of faecal bacteria in receiving surface waters. The model was first validated by comparing model predicted faecal bacteria concentrations with available field measurements. The model simulations agreed well with the observation data. After calibration, the model was applied to investigate the effects of different parameters, including: tidal processes, river discharges from the upstream boundaries and bacteria inputs from the upstream boundaries, wastewater treatment works (WwTWs), rivers and combined sewer overflows (CSO), on the concentrations of faecal bacteria in the Ribble Estuary. The results revealed that the tide and upstream boundary bacteria inputs were the primary factors controlling the distribution of faecal bacteria. The bacteria inputs from the WwTWs in the model domain were generally found not to have a significant impact on distribution of faecal bacteria in the estuary.

Storm loads of culturable and molecular fecal indicators in an inland urban stream

Elevated concentrations of fecal indicator bacteria in receiving waters during wet-weather flows are a considerable public health concern that is likely to be exacerbated by future climate change and urbanization. Knowledge of factors driving the fate and transport of fecal indicator bacteria in stormwater is limited, and even less is known about molecular fecal indicators, which may eventually supplant traditional culturable indicators. In this study, concentrations and loading rates of both culturable and molecular fecal indicators were quantified throughout six storm events in an instrumented inland urban stream. While both concentrations and loading rates of each fecal indicator increased rapidly during the rising limb of the storm hydrographs, it is the loading rates rather than instantaneous concentrations that provide a better estimate of transport through the stream during the entire storm. Concentrations of general fecal indicators (both culturable and molecular) correlated most highly with each other during storm events but not with the human-associated HF183 Bacteroides marker. Event loads of general fecal indicators most strongly correlated with total runoff volume, maximum discharge, and maximum turbidity, while event loads of HF183 most strongly correlated with the time to peak flow in a hydrograph. These observations suggest that collection of multiple samples during a storm event is critical for accurate predictions of fecal indicator loading rates and total loads during wet-weather flows, which are required for effective watershed management. In addition, existing predictive models based on general fecal indicators may not be sufficient to predict source-specific genetic markers of fecal contamination.

Factors affecting the presence of human-associated and fecal indicator real-time quantitative PCR genetic markers in urban-impacted recreational beaches

Urban runoff can carry a variety of pollutants into recreational beaches, often including bacterial pathogens and indicators of fecal contamination. To develop complete recreational criteria and risk assessments, it is necessary to understand conditions under which human contamination could be present at beaches solely impacted by urban runoff. Accurately estimating risk requires understanding sources, concentrations, and transport mechanisms of microbial contaminants in these environments. By applying microbial source tracking methods and empirical modeling, we assessed the presence and level of human contamination at urban runoff impacted recreational beaches. We also identified environmental parameters and pollution sources that can influence the concentration and transport of culturable and molecular fecal indicator bacteria (FIB) in systems impacted solely by urban runoff. Water samples and physico–chemical parameters were collected from shoreline locations from three South Carolina (SC) beaches (five locations per beach) and two Florida (FL) beaches (three locations per beach). Each SC beach was directly impacted by swashes or tidal creeks receiving stormwater runoff from the urbanized area and therefore were designated as swash drain associated (SDA) beaches, while FL beaches were designated as non-swash drain associated (NSDA). Sampling in swash drains (SD; three sites per SD) directly impacting each SC beach was also conducted. Results indicate that although culturable (enterococci) and real-time quantitative polymerase chain reaction (qPCR) (EC23S857, Entero1, and GenBac3) FIB concentrations were, on average, higher at SD locations, SDA beaches did not have consistently higher molecular FIB signals compared to NSDA beaches. Both human-associated markers (HF183 and HumM2) were concomitantly found only at SDA beaches. Bacteroidales species-specific qPCR markers (BsteriF1 and BuniF2) identified differences in the Bacteroidales community, depending on beach type. The marker for general Bacteroidales was most abundant at SD locations and exhibited a high correlation with both culturable and other molecular markers. Combining molecular information with predictive modeling allowed us to identify both alongshore movement of currents and SD outflow as significant influences on the concentration of molecular and culturable indicators in the bathing zone. Data also suggests that combining methodologies is a useful and cost effective approach to help understand transport dynamics of fecal contamination and identify potential sources of contamination at marine beaches.

Fecal bacterial losses in runoff from conventional and no-till pearl millet fertilized with broiler litter

Georgia farmers are increasing preemergence applications of soil residual herbicides to control glyphosate resistant weeds. To improve efficacy these herbicides are often activated by post-application irrigation. Broiler litter is commonly applied to fields before these herbicides. The herbicide wetting-in practice increases surface soil water content and may increase runoff and transport of broiler litter borne fecal bacteria into surface waters during subsequent storm events. Our objective was to determine differences in loads of fecal bacteria, Escherichia coli and Salmonella spp., in runoff from conventional tillage (CT) and no-till (NT) systems after herbicides were watered into an Ultisol fertilized with broiler litter. On replicated 6m2-plots (n=3) simulated rainfall was applied for 70min with composite runoff samples collected every 5min and analyzed for E. coli and Salmonella spp. Although total runoff volume from the CT plots was significantly greater than from NT plots, no significant differences in total load of E. coli and Salmonella or the percent of total loads of E. coli and Salmonella recovered in runoff between tillage systems were observed. Total percentage of Salmonella recovered in runoff from both tillage systems was, however, four log10 orders of magnitude greater than the percentage of E. coli that was recovered. Difference in percentage recovered between the fecal indicator bacterium, E. coli, and the pathogen, Salmonella, underscores an apparent difference in hydrologic transport characteristics of these two fecal bacteria and casts doubts on the efficacy of E. coli as an indicator of risk to public health.