A water quality modeling study of non-point sources at recreational marine beaches

Uncertainty assessment for three-dimensional hydrodynamic and fecal coliform modeling in the Danshuei River estuarine system: The influence of first-order parametric decay reaction

Modeling fecal contamination in water bodies is of importance for microbiological risk assessment and management. This study investigated the transport of fecal coliform (e.g., up to 2.1 × 10⁶ CFU/100 ml at the Zhongshan Bridge due to the main point source from the Xinhai Bridge) in the Danshuei River estuarine system, Taiwan with the main focus on assessing model uncertainty due to three relevant parameters for the microbial decay process. First, a 3D hydrodynamic-fecal coliform model (i.e., SCHISM-FC) was developed and rigorously validated against the available data of water level, velocity, salinity, suspended sediment and fecal coliform measured in 2019. Subsequently, the variation ranges of decay reaction parameters were considered from several previous studies and properly determined using the Monte Carlo simulations. Our analysis showed that the constant ratio of solar radiation (α) as well as the settling velocity (v_s) had the normally-distributed variations while the attachment fraction of fecal coliform bacteria (F_p) was best fitted by the Weibull distribution. The modeled fecal coliform concentrations near the upstream (or downstream) stations were less sensitive to those parameter variations (see the smallest width of confidence interval about 1660 CFU/100 ml at the Zhongzheng Bridge station) due to the dominant effects of inflow discharge (or tides). On the other hand, for the middle parts of Danshuei River where complicated hydrodynamic circulation and decay reaction occurred, the variations of parameters led to much larger uncertainty in modeled fecal coliform concentration (see a wider confidence interval about 117,000 CFU/100 ml at the Bailing Bridge station). Overall, more detailed information revealed in this study would be helpful while the environmental authority needs to develop a proper strategy for water quality assessment and management. Owing to the uncertain decay parameters, for instance, the modeled fecal coliform impacts at Bailing Bridge over the study period showed a 25 % difference between the lowest and highest concentrations at several moments. For the detection of pollution occurrence, the highest to lowest probabilities for a required fecal coliform concentration (e.g., 260,000 CFU/100 ml over the environmental regulation) at Bailing Bridge was possibly greater than three.

Environmental risk assessment for fecal contamination sources in urban and peri-urban estuaries, in Escambia and Santa Rosa counties, FL, USA

Fecal pollution of estuaries and adjacent creeks and streams is of significant concern along the Gulf of Mexico. The prospective threat to human life and water quality impairment via fecal pollution is a substantial danger to the strength and resistance of coastline areas. Pensacola, FL, has a prosperous coastal tourism industry that is utilized for numerous other uses, such as recreational watersports and boating, seafood, and shellfish harvesting. However, the frequency and severity of fecal contamination present possible socio-economic issues, specifically financial hardships. Therefore, understanding the source, abundance, and fate of fecal microbial pollutants in aquatic systems signifies an imperative initial stage for detecting the host sources and techniques to lessen their transport from the landscape. This research aimed to quantify the fecal indicator bacteria (FIB), Escherichia coli, and perform microbiological fecal source tracking to verify if the fecal inputs are of either animal or human host origin. Surface water samples were taken from urban and peri-urban creeks for two sampling periods (February 2021 and January 2022), and IDEXX Colilert-18 (USEPA Standard Method 9223) was used for E. coli enumeration. DNA extractions were obtained from each sample, and quantitative PCR was utilized for fecal microbial source tracking (MST) to detect human, dog, ruminant, and bird host-specific Bacteroides DNA. The result indicates elevated quantities of FIB, E. coli, that surpass the threshold considered safe regarding human health. E. coli at six sites over the two sampling periods exceeded the impairment threshold, reaching as high as 866.4 MPN/100 ml. Fecal source tracking identified human host fecal contamination at four of nine sites, dogs at three of nine, and birds at one site. However, those sites with sources identified via MST all had E. coli levels below impairment thresholds. No sites were determined to be positive for ruminant as a source or for the pathogen Helicobacter pylori. No canine host fecal inputs were found in January 2022, and only one site with human sewage. Our results highlight the utility of MST in assessing bacterial inputs to water bodies and the challenges.

Positive effect of a canal system and reservoir group on the spatial-temporal redistribution of water resources in a pinnate drainage pattern

The uneven spatial and temporal distribution of water resources in pinnate drainage patterns is a major problem worldwide. As scattered components of water conservancy projects, systems of canals and groups of reservoirs in a basin can redistribute water resources in time and space to solve problems. This redistribution effectively avoids the environmental impact inherent in centralized water conservancy projects. In this study, we focused on a network of 88 reservoirs and 675 km of canals in a basin with a pinnate drainage pattern. The discharge of the trunk stream in the basin was calculated in natural, present and forecasted conditions based on the hydrological frequency curve. Then, the hydrodynamics of the trunk stream were simulated by the HEC-RAS model. Furthermore, we analysed the temporal and spatial distribution of water resources in five zones in the basin by Morlet wavelet analysis to determine the balance between water supply and demand. The results demonstrated that the river catchment in the basin changed periodically over periods of 1 year, 8 years and 18 years, as affected by the reservoir groups. The canal system played a major role in water resource transport in the five zones in the basin. The joint action of the reservoir group and canal system reduced the gap between the supply and demand water balance from 27.11% to 0.89%. This study focused on the influence of decentralized water conservancy projects on the spatial and temporal distribution of water resources and provides ideas for solving the problem of water resource allocation in the studied basin.

Numerical Modeling of Microbial Fate and Transport in Natural Waters: Review and Implications for Normal and Extreme Storm Events

Degradation of water quality in recreational areas can be a substantial public health concern. Models can help beach managers make contemporaneous decisions to protect public health at recreational areas, via the use of microbial fate and transport simulation. Approaches to modeling microbial fate and transport vary widely in response to local hydrometeorological contexts, but many parameterizations include terms for base mortality, solar inactivation, and sedimentation of microbial contaminants. Models using these parameterizations can predict up to 87% of variation in observed microbial concentrations in nearshore water, with root mean squared errors ranging from 0.41 to 5.37 log10 Colony Forming Units (CFU) 100 mL−1. This indicates that some models predict microbial fate and transport more reliably than others and that there remains room for model improvement across the board. Model refinement will be integral to microbial fate and transport simulation in the face of less readily observable processes affecting water quality in nearshore areas. Management of contamination phenomena such as the release of storm-associated river plumes and the exchange of contaminants between water and sand at the beach can benefit greatly from optimized fate and transport modeling in the absence of directly observable data.

Assessment for oil spill chemicals: Current knowledge, data gaps, and uncertainties addressing human physical health risk

Limited models are available to estimate human physical health risks (e.g., probability of outcomes such as lung disease, cancer, skin disease) from exposure to chemicals resulting from oil spills that may occur offshore and later impact coastline spills. An approach is presented to assess physical health risks from oil spills that involves establishing a platform capable of assessing aggregate health risk (via inhalation, ingestion, and dermal exposure routes). Gaps include the need to develop models reflecting oil spill concentration distributions given the influence from environmental, physical, biological and chemical factors. Human activities need to be quantified for different populations including emergency response workers, fishermen, shellfish consumers, and children who play at beaches that may be impacted by oil spills. Work is also needed in developing comprehensive toxicological profiles for the majority of chemicals - including dispersants found in oil spills - and to estimate toxicity from mixtures.

Relationship between Coliform Bacteria and Water Quality Factors at Weir Stations in the Nakdong River, South Korea

Artificial structures installed in rivers can change the natural physical, physiochemical, and biological characteristics of the rivers. Coliform bacteria are important water quality indicators, related to human health. This study investigated the relationship between coliform bacteria and water quality factors at eight weir stations constructed in the Nakdong River, a major river in South Korea. Fifteen water quality factors were analyzed at these sites from 2012 to 2016 using correlation and multiple regression analyses. The results for all stations confirmed the analytical validity, with high adjusted R2 values of approximately 0.6 and 0.8 on average for total and fecal coliforms, respectively. The results showed influential water quality factors affecting the concentration of coliform bacteria at weir stations. Specifically, total coliforms were mostly affected by organic matter and fecal coliforms were mostly affected by phosphate phosphorus and suspended solids. Rainfall was the most influential factor affecting both coliforms. Further, both coliforms were negatively affected by organic matter below the Dalseong weir in the mid- to downstream area of the Nakdong River. A positive relationship with phosphate phosphorus was indicated at all weir stations. To the authors’ knowledge, this kind of study has never been attempted so far. Thus, the study results can provide important information on influential water quality factors related to coliform bacteria, especially in the Nakdong River, creating a foundation for future water quality management.

Impact of Climate Forecasts on the Microbial Quality of a Drinking Water Source in Norway Using Hydrodynamic Modeling

This study applies hydrodynamic and water quality modeling to evaluate the potential effects of local climate projections on the mixing conditions in Lake Brusdalsvatnet in Norway and the implications on the occurrence of Escherichia coli (E. coli) at the raw water intake point of the Ålesund water treatment plant in the future. The study is mainly based on observed and projected temperature, the number of E. coli in the tributaries of the lake and projected flow. The results indicate a gradual rise in the temperature of water at the intake point from the base year 2017 to year 2075. In the future, vertical circulations in spring may occur earlier while autumn circulation may start later than currently observed in the lake. The number of E. coli at the intake point of the lake is expected to marginally increase in future. By the year 2075, the models predict an approximately three-fold increase in average E. coli numbers for the spring and autumn seasons compared to current levels. The results are expected to provide the water supply system managers of Ålesund with the information necessary for long-term planning and decisions in the protection of the drinking water source. The method used here can also be applied to similar drinking water sources in Norway for developing effective risk management strategies within their catchments.

Evaluation of the immune responses of the brown mussel Perna perna as indicators of fecal pollution

The mussel Perna perna is an intertidal bivalve that is widely distributed, cultivated and consumed in South Africa, Brazil and Venezuela. Among marine resources, bivalve mollusks are one of the most impacted by anthropogenic pollution, as they can accumulate pathogenic bacteria and water pollutants. Hemocytes are molluscan defense cells, and their abundance and functions can be affected in response to contaminants, such as bacterial load. However, no previous study has investigated the immune response of P. perna hemocytes. The aim of this study was to evaluate several immune parameters in P. perna as indicators of fecal pollution in mussel hemolymph and in seawater. We collected mussels and adjacent seawater from beaches with different levels of fecal contamination in Rio de Janeiro state (Brazil): Vermelha Beach (VB); Icaraí Beach (IB); Urca Beach (UB); and Jurujuba Beach (JB). Hemocyte parameters (density, morphology, phagocytic activity and production of Reactive Oxygen Species - ROS) were evaluated using flow cytometry. We quantified Fecal Indicator Bacteria (FIB) in seawater by the multiple tubes technique for each beach and for hemolymph by the spread-plate technique. In agreement with historical evaluation of fecal contamination levels, UB presented the highest FIB abundance in seawater (thermotolerant coliforms, TEC = 1600 NMP 100 mL^-1), whereas VB exhibited the lowest (TEC = 17 NMP 100 mL^-1). UB mussels had six and eight times higher hemocyte density and phagocytic activity, respectively, than mussels from VB. Mussels from VB and IB presented a significantly lower number of total coliforms in hemolymph and a significantly higher relative internal complexity of hemocytes than those from UB and JB (p ≤ 0.01, PERMANOVA). ROS production by hemocytes was significantly lower in mussels from VB compared to those from JB (p = 0.04, ANOVA). Our results indicate a significant relationship between the level of fecal contamination in aquatic environments and the immune response of mussel hemocytes. Immune-related parameters may therefore be useful as indicators of bivalve health and environmental quality. Our flow cytometric analysis of P. perna hemocytes represents a new approach for studying Perna perna biology and might represent a novel tool for measuring organic pollution and water quality.

Development of a Nowcasting System Using Machine Learning Approaches to Predict Fecal Contamination Levels at Recreational Beaches in Korea

Microbial contamination in beach water poses a public health threat due to waterborne diseases. To reduce the risk of exposure to fecal contamination, informing beachgoers in advance about the microbial water quality is important. Currently, determining the level of fecal contamination takes 24 h. The objective of this study is to predict the current level of fecal contamination (enterococcus [ENT] and ) using readily available environmental variables. Artificial neural network (ANN) and support vector regression (SVR) models were constructed using data from the Haeundae and Gwangalli Beaches in Busan City. The input variables included the tidal level, air and water temperature, solar radiation, wind direction and velocity, precipitation, discharge from the wastewater treatment plant, and suspended solid concentration in beach water. The dependence of fecal contamination on the input variables was statistically evaluated; precipitation, discharge from the wastewater treatment plant, and wind direction at the two beaches were positively correlated to the changes in the two bacterial concentrations ( < 0.01), whereas solar radiation was negatively correlated ( < 0.01). The performance of the ANN model for predicting ENT and at Gwangalli Beach was significantly higher than that of the SVR model with the training dataset ( < 0.05). Based on the comparison of residual values between the predicted and observed fecal indicator bacteria concentrations in two models, the ANN demonstrated better performance than SVR. This study suggests an effective prediction method to determine whether a beach is safe for recreational use.

Developing, cross-validating and applying regression models to predict the concentrations of faecal indicator organisms in coastal waters under different environmental scenarios

This study developed, cross-validated and applied a regression-based model to predict concentrations of faecal indicator organisms (FIOs) under different environmental conditions in the North and South bays of Santa Catarina, South of Brazil. The model was developed using a database of FIO concentrations in seawater sampled at 50 sites and the validation was performed using a different database by comparing 288 pairs of measured and modelled results for 15 sites. The index of agreement between the model outputs and the FIO concentrations measured during the validation period was 66%; the mean average error was 0.43 log₁₀ and the root mean square error was 0.58 log₁₀ MPN.100mL^-1. These validation results indicate that the model provides a fair representation of the FIO contamination in the bays for the meteorological conditions under which the model was trained. The simulation of different scenarios showed that under typical levels of resident human population in the catchments and median rainfall and solar radiation conditions, the median FIO concentration in the bays is 0.4 MPN.100mL^-1. Under extreme meteorological conditions, the combined effect of high rainfall and low solar radiation increased FIO concentrations up to 5 log₁₀ MPN.100mL^-1. The simulated scenarios also show that increases in resident population during the summer tourist season and average rainfall concentrations do not increase median FIO concentrations in the bays relative to periods of time with average population, possibly because of higher bacterial die-off in the waters. The models can be an effective tool for management of human health risks in bathing and shellfish waters impacted by sewage pollution.

Temporal variations analyses and predictive modeling of microbiological seawater quality

Bathing water quality is a major public health issue, especially for tourism-oriented regions. Currently used methods within EU allow at least a 2.2 day period for obtaining the analytical results, making outdated the information forwarded to the public. Obtained results and beach assessment are influenced by the temporal and spatial characteristics of sample collection, and numerous environmental parameters, as well as by differences of official water standards. This paper examines the temporal variation of microbiological parameters during the day, as well as the influence of the sampling hour, on decision processes in the management of the beach. Apart from the fecal indicators stipulated by the EU Bathing Water Directive (E. coli and enterococci), additional fecal (C. perfringens) and non-fecal (S. aureus and P. aeriginosa) parameters were analyzed. Moreover, the effects of applying different evaluation criteria (national, EU and U.S. EPA) to beach ranking were studied, and the most common reasons for exceeding water-quality standards were investigated. In order to upgrade routine monitoring, a predictive statistical model was developed. The highest concentrations of fecal indicators were recorded early in the morning (6 AM) due to the lack of solar radiation during the night period. When compared to enterococci, E. coli criteria appears to be more stringent for the detection of fecal pollution. In comparison to EU and U.S. EPA criteria, Croatian national evaluation criteria provide stricter public health standards. Solar radiation and precipitation were the predominant environmental parameters affecting beach water quality, and these parameters were included in the predictive model setup. Predictive models revealed great potential for the monitoring of recreational water bodies, and with further development can become a useful tool for the improvement of public health protection.

Investigating the fate and transport of fecal coliform contamination in a tidal estuarine system using a three-dimensional model

A three-dimensional fecal coliform transport model was developed and incorporated into a hydrodynamic and suspended sediment transport model to better understand the microbiological water quality in the tidal Tamsui River estuarine system of northern Taiwan, which includes three main tributaries: Dahan River, Xindian River, and Keelung River. The model was calibrated using the water level, salinity, suspended sediment concentration, and fecal coliform data measured in 2010. The predictive skill, a statistical approach, is used to evaluate the model performance. There was quantitatively good agreement between the simulation and measurement results. Further, the calibrated model underwent model sensitivity analysis by varying the model parameters which include the settling velocity, darkness decay rate, partition coefficient, and fecal coliform concentration in the sediment bed. The results indicated that the settling velocity played the most important role in affecting fecal coliform concentrations followed by partition coefficient, darkness decay rate, and fecal coliform concentration in the sediment bed. The model was also used to investigate the effects of salinity and suspended sediment on fecal coliform contamination. The salinity module was excluded in the simulations, resulting in an increase of fecal coliform concentration. However the effect of salinity on fecal coliform concentration is minor. If the suspended sediment transport was excluded in the simulations, the predicted results of fecal coliform concentration decrease to be underestimated the measured data. The modeling results revealed that the inclusion of the suspended sediment transport model in the simulations was of crucial importance because the fecal coliform concentrations were significantly influenced by the suspended sediment concentration in the estuarine system.

Monitoring bacterial indicators of water quality in a tidally influenced delta: A Sisyphean pursuit

The Sacramento-San Joaquin Delta Estuary (Delta) is the confluence of two major watersheds draining the Western Sierra Nevada mountains into the Central Valley of California, ultimately terminating into San Francisco Bay. We sampled 88 sites once a month for two years (2006-2008) over 87 separate sampling events for a total of 1740 samples. Water samples were analyzed for fecal indicator bacteria (Escherichia coli, enterococci and fecal coliforms), and 53 other physiochemical, land use, and environmental characteristics. The purpose of the study was to create a baseline of microbial water quality in the Delta and to identify various factors (climatic, land use, tidal, etc.) that were associated with elevated concentrations of indicator bacteria. Fecal indicator bacteria generally had weak to modest relationships to environmental conditions; the strength and direction of which varied for each microbial indicator, drainage region, and across seasons. Measured and unmeasured, site-specific effects accounted for large portions of variance in model predictions (ρ=0.086 to 0.255), indicating that spatial autocorrelation was a major component of water quality outcomes. The effects of tidal cycling and lack of connectivity between waterways and surrounding landscapes likely contributed to the lack of association between local land uses and microbial outcomes, though weak associations may also be indicative of mismatched spatiotemporal scales. The complex nature of this system necessitates continued monitoring and regular updates to statistical models designed to predict microbial water quality.

Spatial and temporal microbial pollution patterns in a tropical estuary during high and low river flow conditions

Spatial and temporal patterns of coastal microbial pollution are not well documented. Our study examined these patterns through measurements of fecal indicator bacteria (FIB), nutrients, and physiochemical parameters in Hilo Bay, Hawai'i, during high and low river flow. >40% of samples tested positive for the human-associated Bacteroides marker, with highest percentages near rivers. Other FIB were also higher near rivers, but only Clostridium perfringens concentrations were related to discharge. During storms, FIB concentrations were three times to an order of magnitude higher, and increased with decreasing salinity and water temperature, and increasing turbidity. These relationships and high spatial resolution data for these parameters were used to create Enterococcus spp. and C. perfringens maps that predicted exceedances with 64% and 95% accuracy, respectively. Mapping microbial pollution patterns and predicting exceedances is a valuable tool that can improve water quality monitoring and aid in visualizing FIB hotspots for management actions.

Sediment characteristics and microbiological contamination of beach sand - A case-study in the archipelago of Madeira

Beach sand can harbour pathogenic and opportunistic microorganisms, as well as faecal indicator bacteria that influence directly the bathing water quality. Pathogenic and opportunistic microorganisms often raise concern of exposure during beach related recreational activities. In this work, three different types of sandy beaches (natural basaltic, natural calcareous and artificial calcareous) of the Archipelago of Madeira (Portugal) were sampled for bacterial and fungal contaminants and grain size distribution, during four years (2010-2013). Following an extreme weather event in 2010, the faecal indicator bacteria levels spiked, returning to base levels shortly thereafter. The same phenomenon occurred with fungi, where potentially pathogenic fungi were the dominant group. Yeast-like fungi and dermatophytes were, however, mainly associated to months of higher usage by recreational users. Statistical analysis showed higher contamination of sediment in artificial beaches compared to natural beaches and granulometry and chemical composition of sand did not influence in the microbial loads. Instead, bather density and the influence of coastal protection structures needed to maintain the volume of artificial beach sand regarding the removal potential of wave induced currents are obvious influencing factors.

Evaluation of the distribution of fecal indicator bacteria in a river system depending on different types of land use in the southern watershed of the Baltic Sea

The aim of the study was to determine the effects of land use management on changes in the fecal contamination of water in the Łyna River, one of the main lowland watercourses in the southern watershed of the Baltic Sea (northern Poland). A total of 120 water samples were collected in different seasons of 2011 and 2012 at 15 sites where the river intersected forest (FA), agricultural (AA), and urbanized (UA) areas. Fecal indicator bacteria (FIB), the counts of Enterobacteriaceae and Escherichia coli, total bacterial counts (TBCs), and domain Bacteria (EUB338) were determined by culture-dependent and culture-independent methods. Temperature, pH, chemical oxygen demand, dissolved oxygen, total dissolved solids, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, orthophosphate, and total phosphorus were also determined. The lowest bacterial counts were noted in water samples collected in FA, and the highest in samples collected in UA. Statistically significant differences were determined between bacterial populations across the analyzed land use types and in different sampling seasons. Significant correlations were also observed between the populations of FIB and physicochemical parameters. The results indicate that land use type influenced FIB concentrations in river water. The combined use of conventional and molecular methods improves the accuracy of fecal contamination analyses in river ecosystems.

Modeling system for predicting enterococci levels at Holly Beach

This paper presents a new modeling system for nowcasting and forecasting enterococci levels in coastal recreation waters at any time during the day. The modeling system consists of (1) an artificial neural network (ANN) model for predicting the enterococci level at sunrise time, (2) a clear-sky solar radiation and turbidity correction to the ANN model, (3) remote sensing algorithms for turbidity, and (4) nowcasting/forecasting data. The first three components are also unique features of the new modeling system. While the component (1) is useful to beach monitoring programs requiring enterococci levels in early morning, the component (2) in combination with the component (1) makes it possible to predict the bacterial level in beach waters at any time during the day if the data from the components (3) and (4) are available. Therefore, predictions from the component (2) are of primary interest to beachgoers. The modeling system was developed using three years of swimming season data and validated using additional four years of independent data. Testing results showed that (1) the sunrise-time model correctly reproduced 82.63% of the advisories issued in seven years with a false positive rate of 2.65% and a false negative rate of 14.72%, and (2) the new modeling system was capable of predicting the temporal variability in enterococci levels in beach waters, ranging from hourly changes to daily cycles. The results demonstrate the efficacy of the new modeling system in predicting enterococci levels in coastal beach waters. Applications of the modeling system will improve the management of recreational beaches and protection of public health.

A predictive model for microbial counts on beaches where intertidal sand is the primary source

Human health protection at recreational beaches requires accurate and timely information on microbiological conditions to issue advisories. The objective of this study was to develop a new numerical mass balance model for enterococci levels on nonpoint source beaches. The significant advantage of this model is its easy implementation, and it provides a detailed description of the cross-shore distribution of enterococci that is useful for beach management purposes. The performance of the balance model was evaluated by comparing predicted exceedances of a beach advisory threshold value to field data, and to a traditional regression model. Both the balance model and regression equation predicted approximately 70% the advisories correctly at the knee depth and over 90% at the waist depth. The balance model has the advantage over the regression equation in its ability to simulate spatiotemporal variations of microbial levels, and it is recommended for making more informed management decisions.

Microbial evaluation of sandboxes located in urban area

This paper presents the results of a study on the degree of bacteriological pollution of sandboxes situated in fenced and unfenced housing estates located in an urban area in Olsztyn, Poland. Heterotrophic plate counts (HPC22, HPC37), Enterobacteriaceae, Escherichia coli, Enterococcus spp., Staphylococcus spp. and Clostridium perfringens determined by cultivation and fluorescence in situ hybridization (FISH) methods were used as indicators of the sanitary state. Their maximum number in the sand samples reached values of up to 5.4×10(7), 2.6×10(6), 3.3×10(4), 2.1×10(3), 1.8×10(4), 1.9×10(1) and 1.2×10(4)CFU/g, respectively. It was found that values of culture-independent method were two-four orders greater than those obtained by the cultivation method. Among identified Enterobacteriaceae, Pantoea spp. and Enterobacter cloacae were the most numerous, whereas Escherichia cells were detected only occasionally. Pathogenic bacteria of the genus Salmonella sp. were isolated from sandboxes also when E. coli were absent. Bacteria from Staphylococcus genus were isolated irrespective of the site and time of sampling. Additionally, the presence of molds and yeasts was studied. Maximum counts of these microorganisms amounted to 1.0×10(5) and to 3.5×10(4)CFU/g. Aspergillus, Penicillium, Alternaria and Trichoderma genera were most numerous among molds, whereas Trichosporon was detected most frequently among yeasts. Sandboxes in the fenced housing estate and those located in the area which is not close to trees were less polluted than the sand collected from sandboxes in the unfenced housing estate. Potentially pathogenic bacteria of the genus Salmonella spp. were identified in analyzed sandboxes, also when Toxocara and E. coli were absent. It seems that assessing the contamination of children's play areas basing only on fecal bacteria counts and by monitoring number of parasites' eggs may be insufficient to evaluate microbial pollution of sandboxes and may not fully reflect their safety for children.

Identification of Enterococcus faecium and Enterococcus faecalis as vanC-type Vancomycin-Resistant Enterococci (VRE) from sewage and river water in the provincial city of Miyazaki, Japan

As a first step for assessing the risk to human health posed by vancomycin-resistant enterococci (VRE) in the aquatic environment, we screened sewage and urban river water samples from Miyazaki, Japan for VRE. Because vancomycin-resistant organisms are not as prevalent in sewage and river water as vancomycin-susceptible organisms, the samples were screened by minimum inhibitory concentration test using the vancomycin-supplemented membrane-Enterococcus indoxyl-β-d-glucoside (mEI) agar. The isolates, presumed to be enterococci, were identified using 16S rRNA sequencing analysis. The percentages of VRE isolates screened using 4 μg mL(-1) vancomycin-supplemented mEI agar from sewage and urban river water samples were 12% and 24%, respectively. The vancomycin-resistant genes vanC1 and vanC2/3 were detected in the isolates from both samples by PCR analysis. All enterococci isolates containing vanC1, which is a specific gene for vanC-type of VRE, were identified as Enterococcus casseliflavus/gallinarum. Further, 92% enterococci isolates containing vanC2/3 were identified as E. casseliflavus/gallinarum, the remaining isolates containing vanC2/3 were E. faecium (4%) and E. faecalis (4%). Thereafter, the distribution of E. faecium and E. faecalis, which are the major types of enterococci in humans containing vanC2/3, was observed in the water samples collected.

Modeling fecal coliform contamination in a tidal Danshuei River estuarine system

A three-dimensional fecal coliform transport model was developed and incorporated into a hydrodynamic model to obtain a better understanding of local microbiological water quality in the tidal Danshuei River estuarine system of northern Taiwan. The model was firstly validated with the salinity and fecal coliform data measured in 2010. The concentration comparison showed quantitatively good agreement between the simulation and measurement results. Further, the model was applied to investigate the effects of upstream freshwater discharge variation and fecal coliform loading reduction on the contamination distributions in the tidal estuarine system. The qualitative and quantitative analyses clearly revealed that low freshwater discharge resulted in higher fecal coliform concentration. The fecal coliform loading reduction considerably decreased the contamination along the Danshuei River-Tahan Stream, the Hsintien Stream, and the Keelung River.

Microbes in Beach Sands: Integrating Environment, Ecology and Public Health

Beach sand is a habitat that supports many microbes, including viruses, bacteria, fungi and protozoa (micropsammon). The apparently inhospitable conditions of beach sand environments belie the thriving communities found there. Physical factors, such as water availability and protection from insolation; biological factors, such as competition, predation, and biofilm formation; and nutrient availability all contribute to the characteristics of the micropsammon. Sand microbial communities include autochthonous species/phylotypes indigenous to the environment. Allochthonous microbes, including fecal indicator bacteria (FIB) and waterborne pathogens, are deposited via waves, runoff, air, or animals. The fate of these microbes ranges from death, to transient persistence and/or replication, to establishment of thriving populations (naturalization) and integration in the autochthonous community. Transport of the micropsammon within the habitat occurs both horizontally across the beach, and vertically from the sand surface and ground water table, as well as at various scales including interstitial flow within sand pores, sediment transport for particle-associated microbes, and the large-scale processes of wave action and terrestrial runoff. The concept of beach sand as a microbial habitat and reservoir of FIB and pathogens has begun to influence our thinking about human health effects associated with sand exposure and recreational water use. A variety of pathogens have been reported from beach sands, and recent epidemiology studies have found some evidence of health risks associated with sand exposure. Persistent or replicating populations of FIB and enteric pathogens have consequences for watershed/beach management strategies and regulatory standards for safe beaches. This review summarizes our understanding of the community structure, ecology, fate, transport, and public health implications of microbes in beach sand. It concludes with recommendations for future work in this vastly under-studied area.

Impact of rainfall on the hygienic quality of blue mussels and water in urban areas in the Inner Oslofjord, Norway

The effects of precipitation on the hygienic quality of water and blue mussels collected from five different localities in the urban areas in the Inner Oslofjord were investigated, with samples analysed for Escherichia coli, Salmonella spp., pathogenic Vibrio spp., Norovirus, Sapovirus, Cryptosporidium spp. and Giardia duodenalis. The sampling sites were located at varying distances from the outlet of combined sewer overflows (CSO)-impacted rivers/streams. In general, 1-3 log₁₀ increases in fecal indicator bacteria and human pathogens were observed after heavy rainfalls. Blue mussels appeared to be a useful indicator of the impact of sewage at these sites, and generally a good correlation was identified between concentrations of E. coli and other human pathogens in the mussels. Provision of general advice to the public of avoiding areas near the outlets of CSO-impacted rivers after heavy rainfall may reduce the risk of gastroenteritis by bathers and others that may swallow water during recreational activities.

Analysis of water quality and circulation of four recreational Miami beaches through the use of Lagrangian Coherent Structures

Four popular, recreational beaches in Miami, FL are Hobie Beach, Virginia Key Beach, Crandon Park Beach, and Bill Baggs Cape Florida State Park. While all of the beaches are within a few miles of each other in Biscayne Bay, they have greatly differing water qualities, as determined by the testing for fecal indicator bacteria performed by the Florida Department of Health. Using the geodesic theory of transport barriers, we identify Lagrangian Coherent Structures (LCSs) in each area. We show how these material curves, which shape circulation and mixing patterns, can be used to explain the incongruous states of the water at beaches that should be comparable. The LCSs are computed using a hydrodynamic model and verified through field experimentation at each beach.

Comparison of bacterial communities in sands and water at beaches with bacterial water quality violations

Recreational water quality, as measured by culturable fecal indicator bacteria (FIB), may be influenced by persistent populations of these bacteria in local sands or wrack, in addition to varied fecal inputs from human and/or animal sources. In this study, pyrosequencing was used to generate short sequence tags of the 16S hypervariable region ribosomal DNA from shallow water samples and from sand samples collected at the high tide line and at the intertidal water line at sites with and without FIB exceedance events. These data were used to examine the sand and water bacterial communities to assess the similarity between samples, and to determine the impact of water quality exceedance events on the community composition. Sequences belonging to a group of bacteria previously identified as alternative fecal indicators were also analyzed in relationship to water quality violation events. We found that sand and water samples hosted distinctly different overall bacterial communities, and there was greater similarity in the community composition between coastal water samples from two distant sites. The dissimilarity between high tide and intertidal sand bacterial communities, although more similar to each other than to water, corresponded to greater tidal range between the samples. Within the group of alternative fecal indicators greater similarity was observed within sand and water from the same site, likely reflecting the anthropogenic contribution at each beach. This study supports the growing evidence that community-based molecular tools can be leveraged to identify the sources and potential impact of fecal pollution in the environment, and furthermore suggests that a more diverse bacterial community in beach sand and water may reflect a less contaminated site and better water quality.

Integrated modelling of faecal contamination in a densely populated river-sea continuum (Scheldt River and Estuary)

In order to simulate the long-term (months-years) median Escherichia coli distributions and variations in the tidal Scheldt River and Estuary, a dedicated module was developed for the Second-generation Louvain-la-Neuve Ice-ocean Model (SLIM, www.climate.be/slim). The resulting model (SLIM-EC2) presents two specific and new features compared to the older SLIM-EC model version. The first is that the E. coli concentrations in the river are split in three fractions: the free E. coli in the water column, the ones attached to suspended solids and those present in the bottom sediments, each with their own transport, decay and settling-resuspension dynamics. The bacteria attached to particles can settle and survive on the bottom, where they can be brought back in the water column during resuspension events. The second new feature of the model is that it is coupled to the catchment model SENEQUE-EC, which thus provides upstream boundary conditions to SLIM-EC2. The result is an integrated and multi-scale model of the whole Scheldt drainage network from its source down to the Belgian/Dutch coastal zone. This new model reproduces the long-term median E. coli concentration along the Scheldt River and Estuary. An extensive sensitivity study is performed demonstrating the relative robustness of the model with respect to the chosen parameterisations. In addition to reproducing the observed E. coli concentrations in 2007-2008 at various stations, two extreme wastewater management scenarios were considered. Overall, there is no doubt that the Scheldt Estuary acts as a cleaning filter of faecal contamination originating from large Belgian cities. As a result, at the mouth of the Scheldt Estuary E. coli concentration is negligible in all investigated conditions.

Effects of full-scale beach renovation on fecal indicator levels in shoreline sand and water

Recolonization of enterococci, at a non-point source beach known to contain high background levels of bacteria, was studied after a full-scale beach renovation project. The renovation involved importation of new exogenous sand, in addition to infrastructure improvements. The study's objectives were to document changes in sand and water quality and to evaluate the relative contribution of different renovation activities towards these changes. These objectives were addressed: by measuring enterococci levels in the sand and fecal indicator bacteria levels (enterococci and fecal coliform) in the water, by documenting sediment characteristics (mineralogy and biofilm levels), and by estimating changes in observable enterococci loads. Analysis of enterococci levels on surface sand and within sediment depth cores were significantly higher prior to beach renovation (6.3-72 CFU/g for each sampling day) when compared to levels during and after beach renovation (0.8-12 CFU/g) (P < 0.01). During the renovation process, sand enterococci levels were frequently below detection limits (<0.1 CFU/g). For water, exceedances in the regulatory thresholds that would trigger a beach advisory decreased by 40% for enterococci and by 90% for fecal coliform. Factors that did not change significantly between pre- and post- renovation included the enterococci loads from animals (approx. 3 × 10(11) CFU per month). Factors that were observed to change between pre- and post- renovation activities included: the composition of the beach sand (64% versus 98% quartz, and a significant decrease in biofilm levels) and loads from direct stormwater inputs (reduction of 3 × 10(11) CFU per month). Overall, this study supports that beach renovation activities contributed to improved sand and water quality resulting in a 50% decrease of observable enterococci loads due to upgrades to the stormwater infrastructure. Of interest was that the change in the sand mineralogy also coincided with changes in biofilm levels. More work is needed to evaluate the relationships between beach sand mineralogy, biofilm characteristics, and the retention of fecal indicator bacteria in sand.

Performance evaluation of canine-associated Bacteroidales assays in a multi-laboratory comparison study

The contribution of fecal pollution from dogs in urbanized areas can be significant and is an often underestimated problem. Microbial source tracking methods (MST) utilizing quantitative PCR of dog-associated gene sequences encoding 16S rRNA of Bacteroidales are a useful tool to estimate these contributions. However, data about the performance of available assays are scarce. The results of a multi-laboratory study testing two assays for the determination of dog-associated Bacteroidales (DogBact and BacCan-UCD) on 64 single and mixed fecal source samples created from pooled fecal samples collected in California are presented here. Standardization of qPCR data treatment lowered inter-laboratory variability of sensitivity and specificity results. Both assays exhibited 100% sensitivity. Normalization methods are presented that eliminated random and confirmed non-target responses. The combination of standardized qPCR data treatment, use of normalization via a non-target specific Bacteroidales assay (GenBac3), and application of threshold criteria improved the calculated specificity significantly for both assays. Such measures would reasonably improve MST data interpretation not only for canine-associated assays, but for all qPCR assays used in identifying and monitoring fecal pollution in the environment.

Application of the ReNuMa model in the Sha He river watershed: tools for watershed environmental management

Models and related analytical methods are critical tools for use in modern watershed management. A modeling approach for quantifying the source apportionment of dissolved nitrogen (DN) and associated tools for examining the sensitivity and uncertainty of the model estimates were assessed for the Sha He River (SHR) watershed in China. The Regional Nutrient Management model (ReNuMa) was used to infer the primary sources of DN in the SHR watershed. This model is based on the Generalized Watershed Loading Functions (GWLF) and the Net Anthropogenic Nutrient Input (NANI) framework, modified to improve the characterization of subsurface hydrology and septic system loads. Hydrochemical processes of the SHR watershed, including streamflow, DN load fluxes, and corresponding DN concentration responses, were simulated following calibrations against observations of streamflow and DN fluxes. Uncertainty analyses were conducted with a Monte Carlo analysis to vary model parameters for assessing the associated variations in model outputs. The model performed accurately at the watershed scale and provided estimates of monthly streamflows and nutrient loads as well as DN source apportionments. The simulations identified the dominant contribution of agricultural land use and significant monthly variations. These results provide valuable support for science-based watershed management decisions and indicate the utility of ReNuMa for such applications.

Beach nourishment impacts on bacteriological water quality and phytoplankton bloom dynamics

A beach nourishment with approximately 1/3 fine-grained sediment (fines; particle diameter <63 μm) by mass was performed at Southern California's Border Fields State Park (BFSP). The nourishment was found to briefly (<1 day) increase concentrations of surf-zone fecal indicator bacteria (FIB) above single-sample public health standards [104 most probable number (MPN)·(100 mL)(-1)] but had no effect on phytoplankton. Contamination was constrained to the nourishment site: waters 300 m north or south of the nourishment were always below single-sample and geometric mean [≤ 35 MPN · (100 mL)(-1)] standards. Nourishment fines were identified as a source of the fecal indicator Enterococcus ; correlations between fines and enterococci were significant (p < 0.01), and generalized linear model analysis identified fines as the single best predictor of enterococci. Microcosm experiments and field sampling suggest that the short surf-zone residence times observed for enterococci (e-folding time 4 h) resulted from both rapid, postplacement FIB inactivation and mixing/transport by waves and alongshore currents. Nourishment fines were phosphate-rich/nitrogen-poor and were not correlated with surf-zone phytoplankton concentrations, which may have been nitrogen-limited.

An alternative approach to water regulations for public health protection at bathing beaches

New approaches should be considered as the US Environmental Protection Agency (EPA) moves rapidly to develop new beach monitoring guidelines by the end of 2012, as these guidelines serve as the basis by which states and territories with coasts along the oceans and Great Lakes can then develop and implement monitoring programs for recreational waters. We describe and illustrate one possible approach to beach regulation termed as the “Comprehensive Toolbox within an Approval Process (CTBAP).” The CTBAP consists of three components. The first is a “toolbox” consisting of an inventory of guidelines on monitoring targets, a series of measurement techniques, and guidance to improve water quality through source identification and prevention methods. The second two components are principles of implementation. These include first, “flexibility” to encourage and develop an individualized beach management plan tailored to local conditions and second, “consistency” of this management plan to ensure a consistent national level of public health protection. The results of this approach are illustrated through a case study at a well-studied South Florida recreational marine beach. This case study explores different monitoring targets based on two different health endpoints (skin versus gastrointestinal illness) and recommends a beach regulation program for the study beach that focuses predominately on source prevention.

Physical dynamics controlling variability in nearshore fecal pollution: fecal indicator bacteria as passive particles

We present results from a 5-h field program (HB06) that took place at California's Huntington State Beach. We assessed the importance of physical dynamics in controlling fecal indicator bacteria (FIB) concentrations during HB06 using an individual based model including alongshore advection and cross-shore variable horizontal diffusion. The model was parameterized with physical (waves and currents) and bacterial (Escherichia coli and Enterococcus) observations made during HB06. The model captured surfzone FIB dynamics well (average surfzone model skill: 0.84 {E. coli} and 0.52 {Enterococcus}), but fell short of capturing offshore FIB dynamics. Our analyses support the hypothesis that surfzone FIB variability during HB06 was a consequence of southward advection and diffusion of a patch of FIB originating north of the study area. Offshore FIB may have originated from a different, southern, source. Mortality may account for some of the offshore variability not explained by the physical model.

A multi-beach study of Staphylococcus aureus, MRSA, and enterococci in seawater and beach sand

Incidences of Staphylococcus aureus and methicillin resistant S. aureus (MRSA) have risen worldwide prompting a need to better understand routes of human exposure and whether standard bacterial water quality monitoring practices adequately account for this potential threat. Beach water and sand samples were analyzed during summer months for S. aureus, enterococci, and MRSA at three southern California beaches (Avalon, Doheny, Malibu Surfrider). S. aureus frequently was detected in samples of seawater (59%, n = 328) and beach sand (53%, n = 358). MRSA sometimes was detected in seawater (1.6%, n = 366) and sand (2.7%, n = 366) at relatively low concentrations. Site specific differences were observed, with Avalon Beach presenting the highest concentrations of S. aureus and Malibu Surfrider the lowest in both seawater and sand. S. aureus concentrations in seawater and sand were correlated to each other and to a variety of other parameters. Multiple linear regression on the combined beach data indicated that significant explanatory variables for S. aureus in seawater were S. aureus in sand, water temperature, enterococci in seawater, and the number of swimmers. In sand, S. aureus concentrations were related to S. aureus in seawater, water temperature, enterococci in seawater, and inversely to surf height classification. Only the correlation to water temperature held for individually analyzed beaches and for S. aureus concentrations in both seawater and sand. To provide context for these results, the prevalence of S. aureus in sand was compared to published fomite studies, and results suggested that beach prevalence was similar to that in homes.

Quantitative microbial risk assessment of human illness from exposure to marine beach sand

Currently no U.S. federal guideline is available for assessing risk of illness from sand at recreational sites. The objectives of this study were to compute a reference level guideline for pathogens in beach sand and to compare these reference levels with measurements from a beach impacted by nonpoint sources of contamination. Reference levels were computed using quantitative microbial risk assessment (QMRA) coupled with Monte Carlo simulations. In order to reach an equivalent level of risk of illness as set by the U.S. EPA for marine water exposure (1.9 × 10(-2)), levels would need to be at least about 10 oocysts/g (about 1 oocyst/g for a pica child) for Cryptosporidium, about 5 MPN/g (about 1 MPN/g for pica) for enterovirus, and less than 10(6) CFU/g for S. aureus. Pathogen levels measured in sand at a nonpoint source recreational beach were lower than the reference levels. More research is needed in evaluating risk from yeast and helminth exposures as well as in identifying acceptable levels of risk for skin infections associated with sand exposures.

Relationships between sand and water quality at recreational beaches

Enterococci are used to assess the risk of negative human health impacts from recreational waters. Studies have shown sustained populations of enterococci within sediments of beaches but comprehensive surveys of multiple tidal zones on beaches in a regional area and their relationship to beach management decisions are limited. We sampled three tidal zones on eight South Florida beaches in Miami-Dade and Broward counties and found that enterococci were ubiquitous within South Florida beach sands although their levels varied greatly both among the beaches and between the supratidal, intertidal and subtidal zones. The supratidal sands consistently had significantly higher (p < 0.003) levels of enterococci (average 40 CFU/g dry sand) than the other two zones. Levels of enterococci within the subtidal sand correlated with the average level of enterococci in the water (CFU/100mL) for the season during which samples were collected (r(s) = 0.73). The average sand enterococci content over all the zones on each beach correlated with the average water enterococci levels of the year prior to sand samplings (r(s) = 0.64) as well as the average water enterococci levels for the month after sand samplings (r(s) = 0.54). Results indicate a connection between levels of enterococci in beach water and sands throughout South Florida's beaches and suggest that the sands are one of the predominant reservoirs of enterococci impacting beach water quality. As a result, beaches with lower levels of enterococci in the sand had fewer exceedences relative to beaches with higher levels of sand enterococci. More research should focus on evaluating beach sand quality as a means to predict and regulate marine recreational water quality.