Effects of the nuisance algae, Cladophora, on Escherichia coli at recreational beaches in Wisconsin

Recreational beaches constitute a large part of the 12 billion dollar per year tourism industry in Wisconsin. Beach closures due to microbial contamination are costly in terms of lost tourism revenue and adverse publicity for an area. Escherichia coli (E. coli), is used as an indicator of microbial contamination, as high concentrations of this organism should indicate a recent fecal contamination event that may contain other, more pathogenic, bacteria. An additional problem at many beaches in the state is the nuisance algae, Cladophora. It has been hypothesized that mats of Cladophora may harbor high concentrations of E. coli. Three beaches in Door County, WI were selected for study, based on tourist activity and amounts of algae present. Concentrations of E. coli were higher within Cladophora mats than in surrounding water. Beaches displayed an E. coli concentration gradient in water extending away from the Cladophora mats, although this was not statistically significant. Likewise, the amount of Cladophora observed on a beach did not correlate with E. coli concentrations found in routine beach monitoring samples. More work is needed to determine the impact of mats of Cladophora on beach water quality, as well as likely sources of E. coli found within the mats.     

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

A model study was conducted to understand the influence of non-point sources including bather shedding, animal fecal sources, and near shore sand, as well as the impact of the environmental conditions, on the fate and transport of the indicator microbe, enterococci, at a subtropical recreational marine beach in South Florida. The model was based on an existing finite element hydrodynamic and transport model, with the addition of a first order microbe deactivation function due to solar radiation. Results showed that dog fecal events had a major transient impact (hundreds of Colony Forming Units/100 ml [CFU/100 ml]) on the enterococci concentration in a limited area within several hours, and could partially explain the high concentrations observed at the study beach. Enterococci released from beach sand during high tide caused mildly elevated concentration for a short period of time (ten to twenty of CFU/100 ml initially, reduced to 2 CFU/100 ml within 4 h during sunny weather) similar to the average baseline numbers observed at the beach. Bather shedding resulted in minimal impacts (less than 1 CFU/100 ml), even during crowded holiday weekends. In addition, weak current velocity near the beach shoreline was found to cause longer dwelling times for the elevated concentrations of enterococci, while solar deactivation was found to be a strong factor in reducing these microbial concentrations.     

Influence of sampling depth on Escherichia coli concentrations in beach monitoring

While the US Environmental Protection Agency's (EPA) Beaches Environmental Assessment and Coastal Health (BEACH) Act requires coastal and Great Lakes’ states to implement plans for monitoring bacterial contamination of recreational beach water, exactly how this monitoring should occur has not been regulated. This study examined differences in concentration of Escherichia coli in water collected from different depths and from different horizontal locations across the beach. E. coli concentrations were significantly different (p<0.05), when water from different depths was compared. Sampling water at depths of 30, 60, and 120 cm resulted in significantly lower E. coli concentrations as depth increased. Had the State of Wisconsin chosen to collect beach water monitoring samples at a shallower or deeper depth, numbers of beach closures and the potential risk to public health would have changed substantially. These data imply that a revised and standardized protocol for monitoring beach water should be adopted by all states of a monitoring region to better compare microbial contamination of beaches and protect public health.     

Evidence for localized bacterial loading as the cause of chronic beach closings in a freshwater marina

We conducted a comprehensive regional spatial assessment of bacterial water quality in order to determine the points of entry of fecal pollution into a swimming beach area on Lake Michigan that historically has had numerous water quality advisories for elevated levels of Escherichia coli (E. coli). Intensive, consecutive-day water samples were collected during dry and rainy conditions across multiple shoreline and offshore sites, and E. coli levels were enumerated from these samples. For both dry and rainy days, shoreline sites demonstrated significantly higher E. coli levels than offshore regions. We found that offshore (10-150m from shore) E. coli levels did not exceed 235CFU/100ml in more than 5% of the samples collected for 19 surveys (n=209). In contrast, samples taken at the beach area exceeded 235CFU/100ml in 66% of the samples collected for 43 shoreline surveys (n=675). Locally high E. coli levels coincided with bird presence and stormwater at the swimming beach located within the marina, and were unrelated to E. coli levels in connecting harbor waters. We conclude that beach water quality may be impacted by local, persistent contamination, which may confound routine beach monitoring and prevent the detection of regional pollution from other sources.     

Relationships between human adenoviruses and faecal indicator organisms in European recreational waters

Human adenoviruses (HAdV) may be implicated in some disease outbreaks associated with recreational water exposures, typically in swimming pools. Modern molecular methods can be used to detect HAdV in environmental water samples. During the EU FP6 Project VIROBATHE a database of over 290 HAdV analyses with corresponding faecal indicator organism (FIO) determinations was gathered and used to explore statistical associations between HAdV and FIO results. The FIOs measured were Escherichia coli, intestinal enterococci and somatic coliphage. Statistically significant trends of increasing proportions of HAdV-positive results in categories of increasing FIO concentration were found in freshwater but not seawater samples. The analysis of these trends in freshwater samples was refined, the trends remaining statistically significant when using categories of 0.5 log₁₀ intervals of FIO concentration. Logistic regression models were then developed to predict the probability of a HAdV-positive outcome from FIO concentration. Potential applications of these models to predict the probability of HAdV-positive outcomes from routine FIO determinations used to describe recreational water quality exposures and to classify recreational water quality are discussed.     

Mortality rates of autochthonous and fecal bacteria in natural aquatic ecosystems

Bacterial mortality has been investigated in freshwater (River Seine) and in marine (North Sea) systems using a method based on following the disappearance of radioactivity from the DNA of assemblages of bacteria previously labeled with tritiated thymidine. Measurement of bacterial mortality of autochthonous and various types of fecal bacteria allowed direct comparisons between their respective first-order mortality rates. Mortality rates obtained for the different types of bacteria in the River Seine were, respectively, 7.9-33.9 x 10(-3)h(-1) for Escherichia coli, 12.2-29.2 x 10(-3)h(-1) for S. faecium and 7.0-18.3 x 10(-3)h(-1) for the autochthonous bacteria. In the Belgian coastal waters, these rates were 4.6-27.3 x 10(-3)h(-1) for E. coli, 6.0-22.0 x 10(-3)h(-1) for S. typhimurium, 10.0-18.9 x 10(-3)h(-1) for S. faecium and 1.0-13.9 x 10(-3)h(-1) for autochthonous bacteria. In both environments, the overall mortality rates of autochthonous and the different fecal bacteria were in the same order of magnitude and overall mortality rates of E. coli were on average about twice as high for autochthonous bacteria. Grazing by protozooplankton was the dominant process of mortality for fecal and autochthonous bacteria in both environments. Except in a few situations, grazing by protozooplankton was responsible for more than 90% of the overall mortality rate of fecal and autochthonous bacteria in the river and in the coastal area.     

Population structure of Cladophora-borne Escherichia coli in nearshore water of Lake Michigan

We previously reported that the macrophytic green alga Cladophora harbors high densities (up to 10(6) colony-forming units/g dry weight) of the fecal indicator bacteria, Escherichia coli and enterococci, in shoreline waters of Lake Michigan. However, the population structure and genetic relatedness of Cladophora-borne indicator bacteria remain poorly understood. In this study, 835 E. coli isolates were collected from Cladophora tufts (mats) growing on rocks from a breakwater located within the Indiana Dunes National Lakeshore in northwest Indiana. The horizontal fluorophore enhanced rep-PCR (HFERP) DNA fingerprinting technique was used to determine the genetic relatedness of the isolates to each other and to those in a library of E. coli DNA fingerprints. While the E. coli isolates from Cladophora showed a high degree of genetic relatedness (92% similarity), in most cases, however, the isolates were genetically distinct. The Shannon diversity index for the population was very high (5.39). Both spatial and temporal influences contributed to the genetic diversity. There was a strong association of isolate genotypes by location (79% and 80% for lake- and ditch-side samplings, respectively), and isolates collected from 2002 were distinctly different from those obtained in 2003. Cladophora-borne E. coli isolates represented a unique group, which was distinct from other E. coli isolates in the DNA fingerprint library tested. Taken together, these results indicate that E. coli strains associated with Cladophora may be a recurring source of indicator bacteria to the nearshore beach.     

Detection and remediation of human-origin pollution at two public beaches in Virginia using multiple source tracking methods

Two public beaches (Anderson and Hilton) in Newport News, Virginia, were frequently closed to swimming in 2004 due to high Enterococcus spp. counts that exceeded the regulatory standard. The microbial source tracking (MST) methods of antibiotic resistance analysis (ARA) and fluorometry (to detect optical brighteners) were used in the summer of 2004 to determine the origins of fecal pollution at the two beaches. Both MST methods detected substantial human-origin pollution at the two beaches, in locations producing consistently high levels of Enterococcus spp. Investigations by municipal officials led to the fluorometric detection and subsequent repair of sewage infrastructure problems at both beaches. The success of the mitigation efforts was confirmed during the summer of 2005 using ARA and fluorometry, with the results cross-validated by pulsed-field gel electrophoresis (PFGE).     

Survival dynamics of fecal bacteria in ponds in agricultural watersheds of the Piedmont and Coastal Plain of Georgia

Animal agriculture in watersheds produces manure bacteria that may contaminate surface waters and put public health at risk. We measured fecal indicator bacteria (commensal Escherichia coli and fecal enterococci) and manure pathogens (Salmonella and E. coli 0157:H7), and physical-chemical parameters in pond inflow, within pond, pond outflow, and pond sediments in three ponds in agricultural watersheds. Bishop Pond with perennial inflow and outflow is located in the Piedmont, and Ponds A and C with ephemeral inflow and outflow in the Coastal Plain of Georgia. Bromide and chloride tracer experiments at Bishop Pond reflected a residence time much greater than that estimated by two models, and indicated that complete mixing within Bishop Pond was never obtained. The long residence time meant that fecal bacteria were exposed to solar UV-radiation and microbial predation. At Bishop Pond outflow concentrations of fecal indicator bacteria were significantly less than inflow concentrations; such was not observed at Ponds A and C. Both Salmonella and E. coli 0157:H7 were measured when concomitant concentrations of commensal E. coli were below the criterion for surface water impairment indicating problems with the effectiveness of indicator organisms. Bishop Pond improved down stream water quality; whereas, Ponds A and C with ephemeral inflow and outflow and possibly greater nutrient concentrations within the two ponds appeared to be less effective in improving down stream water quality.     

UV inactivation and characteristics after photoreactivation of Escherichia coli with plasmid: health safety concern about UV disinfection

Occurrence and degree of photoreactivation after ultraviolet (UV) exposure have been widely studied. However, the characteristics of photoreactivated microorganisms were rarely investigated. Hence, in this study, Escherichia coli with plasmids of ampicillin (amp)-resistance or fluorescence was used as indicators to examine the UV inactivation efficiencies and variations of characteristics of E. coli after subsequent photoreactivation.The experimental results indicate that the amp-resistant bacteria and the fluorescent bacteria used in this study had similar trends of UV dose-response curves. 3.5-log₁₀ and 3-log₁₀ reductions were achieved with a UV dose of 5 mJ/cm² for the amp-resistant and fluorescent E. coli, respectively. There was no significant difference in the UV inactivation behavior, as compared with common strains of E. coli.For the amp-resistant E. coli and the fluorescent E. coli, after exposures with UV doses of 5, 15, 25, 40 and 80 mJ/cm², the corresponding percent photoreactivations after a 4 h exposure to photoreactivating light were 1% and 46% respectively for a UV dose of 5 mJ/cm², and essentially negligible for all other UV doses. Furthermore, the photoreactivated amp-resistant bacteria still have the ability of amp-resistance. And the revived fluorescent E. coli showed similar fluorescent behavior, compared with the untreated bacteria. The experimental results imply that after UV inactivation and subsequent photoreactivation, the bacteria retained the initial characteristics coded in the plasmid. This reveals a possibility that some characteristics of bacteria can retain or recover through photoreactivation, and a safety concern about pathogenicity revival might need to be considered with UV disinfection and photoreactivation.     

Growing season surface water loading of fecal indicator organisms within a rural watershed

The loading of microbial contaminants was examined within the Thomas Brook watershed, a 784 ha mixed land-use catchment located in the headwaters of the Cornwallis River drainage basin (Nova Scotia, Canada). The objectives were to: (i) examine spatial and temporal characteristics of fecal bacteria loading during the growing season from five subwatersheds, and (ii) develop areal fecal indicator organism export coefficients for rural landscapes. Fecal coliform, Escherichia coli, total suspended solids (TSS) concentrations and stream flow were monitored at five locations in the watershed over six consecutive growing seasons (May-Oct, 2001-2006). A nested watershed monitoring approach was used to determine bacterial loading from distinct source types (residential vs. agricultural) during both baseflow and stormflow periods. Areal bacterial loading rates increased in each nested watershed moving downstream through the watershed and were highest in the three subcatchments dominated by agricultural activities. Upper watershed bacterial loading throughout the growing season from an agricultural subcatchment (Growing Season Avg 8.92 × 10¹⁰ CFU ha⁻¹) was consistently higher than a residential subcatchment (Growing Season Avg 8.43 × 10⁹ CFU ha⁻¹). As expected, annual average stormflow bacterial loads were higher than baseflow loads, however baseflow loads still comprised between 14 and 35% of the growing season bacterial loads in the five subwatersheds. Fecal bacteria loads were greater during years with higher annual precipitation. A positive linear relationship was observed between E. coli and TSS loading during the 2005 and 2006 growing seasons when both parameters were monitored, indicating that the processes of sediment transport and bacterial transport are linked. It is anticipated that computed areal microbial loading coefficients will be useful in developing watershed management plans. More intensive sampling during stormflow events is recommended for improving these coefficients.     

Persistence of fecal indicator bacteria in Santa Monica Bay beach sediments

Monitoring the water quality of recreational beaches is only one step toward understanding microbial contamination -- the primary cause of beach closings. The surf zone sediment reservoir is typically overlooked and may also be important. This study involved monitoring the fecal indicator bacteria (FIB) levels in water and sediment at three ocean beaches (two exposed and one enclosed) during a storm event, conducting laboratory microcosm experiments with sediment from these beaches, and surveying sediment FIB levels at 13 beaches (some exposed and some enclosed). Peaks in Escherichia coli and enterococci concentrations in water and sediment coincided with storm activity at the two exposed beaches, while levels of both FIB were consistently high and irregular at the enclosed beach. Results from microcosm experiments showing similar, dramatic growth of FIB in both overlying water and sediment from all beaches, as well as results from the beach survey, support the hypothesis that the quiescent environment rather than sediment characteristics can explain the elevated sediment FIB levels observed at enclosed beaches. This work has implications for the predictive value of FIB measurements, and points to the importance of the sediment reservoir.     

Characterization of fecal concentrations in human and other animal sources by physical,culture-based,and quantitative real-time PCR methods

The characteristics of fecal sources, and the ways in which they are measured, can profoundly influence the interpretation of which sources are contaminating a body of water. Although feces from various hosts are known to differ in mass and composition, it is not well understood how those differences compare across fecal sources and how differences depend on characterization methods. This study investigated how nine different fecal characterization methods provide different measures of fecal concentration in water, and how results varied across twelve different fecal pollution sources. Sources investigated included chicken, cow, deer, dog, goose, gull, horse, human, pig, pigeon, septage and sewage. A composite fecal slurry was prepared for each source by mixing feces from 6 to 22 individual samples with artificial freshwater. Fecal concentrations were estimated by physical (wet fecal mass added and total DNA mass extracted), culture-based (Escherichia coli and enterococci by membrane filtration and defined substrate), and quantitative real-time PCR (Bacteroidales, E. coli, and enterococci) characterization methods. The characteristics of each composite fecal slurry and the relationships between physical, culture-based and qPCR-based characteristics varied within and among different fecal sources. An in silico exercise was performed to assess how different characterization methods can impact identification of the dominant fecal pollution source in a mixed source sample. A comparison of simulated 10:90 mixtures based on enterococci by defined substrate predicted a source reversal in 27% of all possible combinations, while mixtures based on E. coli membrane filtration resulted in a reversal 29% of the time. This potential for disagreement in minor or dominant source identification based on different methods of measurement represents an important challenge for water quality managers and researchers.     

Fecal indicator bacteria and Salmonella in ponds managed as bird habitat, San Francisco Bay, California, USA

Throughout the world, coastal resource managers are encouraging the restoration of previously modified coastal habitats back into wetlands and managed ponds for their ecosystem value. Because many coastal wetlands are adjacent to urban centers and waters used for human recreation, it is important to understand how wildlife can affect water quality. We measured fecal indicator bacteria (FIB) concentrations, presence/absence of Salmonella, bird abundance, and physico-chemical parameters in two coastal, managed ponds and adjacent sloughs for 4 weeks during the summer and winter in 2006. We characterized the microbial water quality in these waters relative to state water-quality standards and examined the relationship between FIB, bird abundance, and physico-chemical parameters. A box model approach was utilized to determine the net source or sink of FIB in the ponds during the study periods. FIB concentrations often exceeded state standards, particularly in the summer, and microbial water quality in the sloughs was generally lower than in ponds during both seasons. Specifically, the inflow of water from the sloughs to the ponds during the summer, more so than waterfowl use, appeared to increase the FIB concentrations in the ponds. The box model results suggested that the ponds served as net wetland sources and sinks for FIB, and high bird abundances in the winter likely contributed to net winter source terms for two of the three FIB in both ponds. Eight serovars of the human pathogen Salmonella were isolated from slough and pond waters, although the source of the pathogen to these wetlands was not identified. Thus, it appeared that factors other than bird abundance were most important in modulating FIB concentrations in these ponds.     

Variability of fecal indicator bacteria in flowing and ponded waters in southern California: implications for bacterial TMDL development and implementation

Recreational water quality is assessed by using water quality objectives for fecal indicator bacteria (FIB) including total coliform, fecal coliform (or E. coli), and/or Enterococcus. It is required under the Clean Water Act that a TMDL be developed for a bacteria-impaired water body. The development and implementation of bacterial TMDLs has proven challenging and often difficult due to unknown source(s) of FIB. This study found that FIB levels varied significantly in flowing water, ponded water, and associated sediment. FIB levels in isolated ponded water in waterways were significantly higher than in flowing water. Sediment under ponded water contained a great amount of FIB. Furthermore, FIB concentrations in ponded water tended to increase with increasing water temperature and to decrease with increasing water salinity. The result provides the field evidence of survival/growth of FIB in water and sediment under ambient conditions in southern California. A holistic approach including natural sources (e.g., a reference system) should be considered for practical and applicable purposes while developing and implementing bacterial TMDLs for pathogen-impaired waterbodies.     

Water quality prediction of marine recreational beaches receiving watershed baseflow and stormwater runoff in southern California, USA

Beach advisories are issued to the public in California when the concentration of fecal indicator bacteria (FIB), including total coliform, fecal coliform (or Escherichia coli), and Enterococcus, exceed their recreational water health standards, or when the amount of a rainfall event is above the pre-determined threshold. However, it is not fully understood about how and to what degree stormwater runoff or baseflow exerts impacts on beach water quality. Furthermore, current laboratory methods used to determine the FIB levels take 18-96 h, which is too slow to keep pace with changes in FIB levels in water. Thus, a beach may not be posted when it is contaminated, and may be posted under advisory when bacterial levels have already decreased to within water quality standards. The study was designed to address the above critical issues. There were large temporal and spatial variations in FIB concentrations along two popular State Beaches in San Diego, CA, USA. The rainstorm-induced runoff from the watersheds exerts significant impacts on the marine recreational water quality of the beaches adjacent to lagoons during the first 24-48 h after a rain event. The large volume of stormwater runoff discharging to beaches caused high FIB concentrations in beach water not only at the lagoon outlet channel and the mixing zone, but also at the locations 90 m away from the channel northward or southward along the shoreline. The geomorphology of beach shoreline, distance from the outlet channel, wind strength, wind direction, tide height, wave height, rainfall, time lapse after a rainstorm, or channel flow rate played a role in affecting the distribution of FIB concentrations in beach water. Despite the great temporal and spatial variability of FIB concentrations along a shoreline, the artificial neural network-based models developed in this study are capable of successfully predicting FIB concentrations at different beaches, different locations, and different times under baseflow or rainstorm conditions. The models are based on readily measurable variables including temperature, conductivity, pH, turbidity, channel water flow, rainfall, and/or time lapse after a rainstorm. The established models will help fill the current gap between beach posting and actual water quality and make more meaningful and effective decisions on beach closures and advisories.     

Multi-scale temporal and spatial variation in genotypic composition of Cladophora-borne Escherichia coli populations in Lake Michigan

High concentrations of Escherichia coli in mats of Cladophora in the Great Lakes have raised concern over the continued use of this bacterium as an indicator of microbial water quality. Determining the impacts of these environmentally abundant E. coli, however, necessitates a better understanding of their ecology. In this study, the population structure of 4285 Cladophora-borne E. coli isolates, obtained over multiple three day periods from Lake Michigan Cladophora mats in 2007-2009, was examined by using DNA fingerprint analyses. In contrast to previous studies that have been done using isolates from attached Cladophora obtained over large time scales and distances, the extensive sampling done here on free-floating mats over successive days at multiple sites provided a large dataset that allowed for a detailed examination of changes in population structure over a wide range of spatial and temporal scales. While Cladophora-borne E. coli populations were highly diverse and consisted of many unique isolates, multiple clonal groups were also present and accounted for approximately 33% of all isolates examined. Patterns in population structure were also evident. At the broadest scales, E. coli populations showed some temporal clustering when examined by year, but did not show good spatial distinction among sites. E. coli population structure also showed significant patterns at much finer temporal scales. Populations were distinct on an individual mat basis at a given site, and on individual days within a single mat. Results of these studies indicate that Cladophora-borne E. coli populations consist of a mixture of stable, and possibly naturalized, strains that persist during the life of the mat, and more unique, transient strains that can change over rapid time scales. It is clear that further study of microbial processes at fine spatial and temporal scales is needed, and that caution must be taken when interpolating short term microbial dynamics from results obtained from weekly or monthly samples.     

Occurrence, molecular characterization and antibiogram of water quality indicator bacteria in river water serving a water treatment plant

Water pollution by microorganisms of fecal origin is a current world-wide public health concern. Total coliforms, fecal coliforms (Escherichia coli) and enterococci are indicators commonly used to assess the microbiological safety of water resources. In this study, influent water samples and treated water were collected seasonally from a water treatment plant and two major water wells in a Black Belt county of Alabama and evaluated for water quality indicator bacteria. Influent river water samples serving the treatment plant were positive for total coliforms, fecal coliforms (E. coli), and enterococci. The highest number of total coliform most probable number (MPN) was observed in the winter (847.5 MPN/100 mL) and the lowest number in the summer (385.6 MPN/100 mL). Similarly E. coli MPN was substantially higher in the winter (62.25 MPN/100 mL). Seasonal variation of E. coli MPN in influent river water samples was strongly correlated with color (R² = 0.998) and turbidity (R² = 0.992). Neither E. coli nor other coliform type bacteria were detected in effluent potable water from the treatment plant. The MPN of enterococci was the highest in the fall and the lowest in the winter. Approximately 99.7 and 51.5 enterococci MPN/100 mL were recorded in fall and winter seasons respectively. One-way ANOVA tests revealed significant differences in seasonal variation of total coliforms (P < 0.05), fecal coliforms (P < 0.01) and enterococci (P < 0.01). Treated effluent river water samples and well water samples revealed no enterococci contamination. Representative coliform bacteria selected by differential screening on Coliscan Easygel were identified by 16S ribosomal RNA gene sequence analysis. E. coli isolates were sensitive to gentamicin, trimethoprim/sulfamethazole, ciprofloxacin, vancomycin, tetracycline, ampicillin, cefixime, and nitrofurantoin. Nonetheless, isolate BO-54 displayed decreased sensitivity compared to other E. coli isolates. Antibiotic sensitivity pattern can be employed in microbial source tracking.     

Concentrations of host-specific and generic fecal markers measured by quantitative PCR in raw sewage and fresh animal feces

We measured the concentrations of four host-specific (human, dog, cow, and horse Bacteroidales), four generic fecal (16S total Bacteroidales and Escherichia coli, 23S Enterococcus and uidA E. coli,) and two universal bacterial (16S universal and rpoB universal) DNA targets by qPCR in raw sewage and pooled fecal samples from dogs, cows, horses, and Canada Geese. A spiking protocol using the non-fecal bacterium Pseudomonas syringae pph6 was developed to estimate the recovery of DNA from fecal and environmental samples. The measured fecal marker concentrations were used to calculate baseline ratios and variability of host-specific to generic indicators for each host type. The host-specific markers were found in high concentrations (8-9 log₁₀ copies/g dry wt.) in their respective hosts' samples, which were equal to or greater than the concentrations of generic E. coli and Enterococcus markers, lending support to the use of host-specific and generic Bacteroidales as sensitive indicators of fecal pollution. The host-specific markers formed a consistent percentage of total Bacteroidales in target host feces and raw sewage, with human-specific comprising 82%, dog-specific 6%, cow-specific 4% and horse-specific 2%. Based on this limited data set, the measurement of host-specific indicators by qPCR has several promising applications. These applications include determining the percentage of total Bacteroidales contributed by a specific host type, using the ratios of host-specific markers to E. coli or Enterococcus to estimate the contribution of each source to these regulated fecal indicator bacteria, and estimating the mass of feces from each host type in environmental samples.     

Impact of urbanization and agriculture on the occurrence of bacterial pathogens and stx genes in coastal waterbodies of central California

Fecal pollution enters coastal waters through multiple routes, many of which originate from land-based activities. Runoff from pervious and impervious land surfaces transports pollutants from land to sea and can cause impairment of coastal ocean waters. To understand how land use practices and water characteristics influence concentrations of fecal indicator bacteria (FIB) and pathogens in natural waters, fourteen coastal streams, rivers, and tidal lagoons, surrounded by variable land use and animal densities, were sampled every six weeks over two years (2008 & 2009). Fecal indicator bacteria (FIB; Escherichia coli and Enterococci) and Salmonella concentrations, the occurrence of Bacteroidales human, ruminant, and pig-specific fecal markers, E. coli O157:H7, and Shiga toxin (stx) genes present in E. coli, were measured. In addition, environmental and climatic variables (e.g., temperature, salinity, rainfall), as well as human and livestock population densities and land cover were quantified. Concentrations of FIB and Salmonella were correlated with each other, but the occurrence of host-specific Bacteroidales markers did not correlate with FIB or pathogens. FIB and Salmonella concentrations, as well as the occurrence of E. coli harboring stx genes, were positively associated with the fraction of the surrounding subwatershed that was urban, while the occurrence of E. coli O157:H7 was positively associated with the agricultural fraction. FIB and Salmonella concentrations were negatively correlated to salinity and temperature, and positively correlated to rainfall. Areal loading rates of FIB, Salmonella and E. coli O157:H7 to the coastal ocean were calculated for stream and river sites and varied with land cover, salinity, temperature, and rainfall. Results suggest that FIB and pathogen concentrations are influenced, in part, by their flux from the land, which is exacerbated during rainfall; once waterborne, bacterial persistence is affected by water temperature and salinity.