Sources Of Fecal Indicator Bacteria Research Articles

Dry and Wet Weather Survey for Human Fecal Sources in the San Diego River Watershed

State and federal agencies regulate fecal indicator bacteria (FIB), such as E. coli or Enterococcus, in order to manage public health risks at swimming beaches. Despite these goals, watershed managers are challenged in terms of how to best clean up sources of FIB because concentrations frequently exceed water quality objectives, and sources—both human and nonhuman sources of FIB—appear to be everywhere. Since most nonhuman fecal sources represent substantially lower public health risks than human sources do, this study utilizes the human fecal source marker HF183 to better define watershed managers’ riskiest sites and times in order to prioritize remediation actions. A total of 117 samples were collected and analyzed for both FIB and HF183 from 26 sites during multiple sampling campaigns between 2019 and 2021 along the mainstem in addition to major tributaries in a highly urbanized watershed. The results indicated that the vast majority of samples (96%) quantified HF183 during wet weather, ranging from 99 to 44,768 gene copies/100 mL. Similar to HF183, the FIB results exceeded water quality objectives for 100% of the samples in wet weather; however, HF183 was rarely quantified in dry weather, with 3 of 72 samples (4%) exceeding 500 gene copies/100 mL, while two-thirds of samples (67%) exceeded FIB water quality objectives during dry weather. Where HF183 was detected in dry weather, isolated and unpredictable events explained human fecal pollution. It is more challenging in wet weather to identify and quantify the source(s) of human fecal pollution.

Observations and Correlations from a 3-Year Study of Fecal Indicator Bacteria in the Mohawk River in Upstate NY

Fecal indicator bacteria (FIB), such as E. coli and Enterococci, are used to indicate the potential of fecal contamination in waterways. One known source of FIB in urbanized areas is the occurrence of combined sewer overflows (CSOs). To explore the impact of CSOs on local water quality and FIB presence, sampling was conducted during the summers of 2017–2019 of two cities, one with CSOs and one without, on the Mohawk River in upstate New York, USA. Sampling included in situ physiochemical parameters of pH, temperature, and dissolved oxygen and laboratory tests for E. coli, Enterococci, nitrates, and total organic carbon (TOC). Correlations between parameters were explored using the Wilcoxon rank sum test and Spearman’s Rank correlation with and without considerations of site and city location. Overall, positive correlations between FIB and rainfall were identified in one city but were less significant in the other, suggesting a buffering of FIB concentrations likely due to inflow contributions from a reservoir. Samples collected downstream from an active CSO reached the detection limit of the FIB tests, demonstrating a 2-log or greater increase in FIB concentrations from dry weather conditions. The city with CSOs demonstrated greater FIB concentrations, which are likely a combination of greater urban runoff, CSOs, and the potential resuspension of sediment during high flow events. Due to the widespread presence of FIB in the region, future research includes utilizing microbial source tracking to identify the sources of contamination in the region.

Application of molecular source tracking and mass balance approach to identify potential sources of fecal indicator bacteria in a tropical river.

Microbial source tracking and a mass balance approach were used to identify sources of fecal indicator bacteria (FIB) in the Hanalei River, Kaua’i, Hawai’i. Historically, concentrations enterococci and Clostridium perfringens were significantly higher during storm flows compared to non-storm flows in the Hanalei River, and correlated to total suspended solids in the river. During targeted dry weather studies, the Hanalei River bed sediments and streambank soils were documented to harbor E. coli, enterococci, and the human- and pig-specific fecal markers in Bacteroidales, suggesting that sediments and soils may be potential sources of these microorganisms to the Hanalei river. The human-specific marker in Bacteroidales was four times as likely to be detected in sediment and soil samples as in water samples. Furthermore, the occurrence of host-specific source tracking markers is indicative that a portion of FIB present in the Hanalei River are of fecal origin. A mass balance approach was used to explore causes of observed FIB loadings and losses along different reaches of the river. Resuspension or deposition of FIB-laden river sediments cannot account for changes in E. coli and enterococci concentrations along the river during dry weather. Additionally, losses due to bacterial inactivation were insignificant. Groundwater and ditches draining agricultural and urban lands were shown to provide sufficient FIB fluxes to account for the observed loads along some river reaches. The presence of the human-specific Bacteroidales marker in the river water, sediments and adjacent soils, as well as the presence of the human enterovirus marker in the water, suggests that there is widespread human fecal contamination in the Hanalei River that is likely a result of nearby wastewater disposal systems.

Human Health Risks Associated with Recreational Waters: Preliminary Approach of Integrating Quantitative Microbial Risk Assessment with Microbial Source Tracking

Gastrointestinal (GI) illness risks associated with exposure to waters impacted by human and nonhuman fecal sources were estimated using quantitative microbial risk assessment (QMRA). Microbial source tracking (MST) results had identified Escherichia coli (E. coli) contributors to the waterbody as human and unidentified (10%), cattle and domestic animals (25%), and wildlife (65%) in a rural watershed. The illness risks associated with ingestion during recreation were calculated by assigning reference pathogens for each contributing source and using pathogen dose–response relationships. The risk of GI illness was calculated for a specific sampling site with a geometric mean of E. coli of 163 colony forming units (cfu) 100 mL−1, and the recreational standard of E. coli, 126 cfu 100 mL−1. While the most frequent sources of fecal indicator bacteria at the sampling site were nonhuman, the risk of illness from norovirus, the reference pathogen representing human waste, contributed the greatest risk to human health. This study serves as a preliminary review regarding the potential for incorporating results from library-dependent MST to inform a QMRA for recreational waters. The simulations indicated that identifying the sources contributing to the bacterial impairment is critical to estimate the human health risk associated with recreation in a waterbody.

Patterns of sediment-associated fecal indicator bacteria in an urban estuary: Benthic-pelagic coupling and implications for shoreline water quality

Estuarine and coastal waterways are commonly monitored for fecal and sewage contamination to protect recreator health and ecosystem functions. Such monitoring programs commonly rely on cultivation-based counts of fecal indicator bacteria (FIB) in water column samples. Recent studies demonstrate that sediments and beach sands can be heavily colonized by FIB, and that settling and resuspension of colonized particles may significantly influence the distribution of FIB in the water column. However, measurements of sediment FIB are rarely incorporated into monitoring programs, and geographic surveys of sediment FIB are uncommon. In this study, the distribution of FIB and the extent of benthic-pelagic FIB coupling were examined in the urbanized, lower Hudson River Estuary. Using cultivation-based enumeration, two commonly-measured FIB, enterococci and Escherichia coli, were widely distributed in both sediment and water, and were positively correlated with each other. The taxonomic identity of FIB isolates from water and sediment was confirmed by DNA sequencing. The geometric mean of FIB concentration in sediment was correlated with both the geometric mean of FIB in water samples from the same locations and with sediment organic carbon. These two positive associations likely reflect water as the FIB source for underlying sediments, and longer FIB persistence in the sediments compared to the water, respectively. The relative representation of other fecal associated bacterial genera in sediment, determined by 16S rRNA gene sequencing, increased with the sequence representation of the two FIB, supporting the value of these FIB for assessing sediment contamination. Experimental resuspension of sediment increased shoreline water column FIB concentrations, which may explain why shoreline water samples had higher average FIB concentrations than samples collected nearby but further from shore. In combination, these results demonstrate extensive benthic-pelagic coupling of FIB in an urbanized estuary and highlight the importance of sediment FIB distribution and ecology when interpreting water quality monitoring data.

Importance of soil texture to the fate of pathogens introduced by irrigation with treated wastewater

World-wide water scarcity is urging the use of treated wastewater (TWW) for irrigation but this practice may have adverse effects on soil and crop contamination due to the introduction of potential microbial pathogens. The objective of this study was to evaluate the potential health risks caused by TWW irrigation of soils differing in their texture, i.e., soil particle fractions including sand, silt and clay. We predicted that the presence of fecal indicator bacteria (FIB) and pathogens would not be linked to TWW irrigation, yet their abundance would be favored by the smallest soil fraction (~2 nm, e.g., clay) as it provides the largest surface area. To test our hypotheses, culture dependent and independent techniques were used to monitor the presence, abundance and source of FIB and microbial pathogens (bacteria and protists) in water (TWW and potable water) and three irrigated soil types (clay, loam and loamy-sand) in a field study spanning two years. The results showed that FIB and pathogens' abundance were significantly different between water types, yet these differences did not carry to the irrigated soils. The abundance and presence of FIB and potential opportunistic or obligate human pathogens did not significantly differ (p > 0.05) between TWW and potable water irrigated soils. Moreover, the source of the FIB and potential pathogens could not be linked to irrigation with TWW. Yet, soil type significantly altered the potential pathogens' diversity (p < 0.05) and abundance (p < 0.05), and differences were affected by clay content, as predicted. The results gave no indication for potential adverse health effects associated with the application of TWW but demonstrated that clay has a particular stabilizing effect on the potential presence of microbial pathogens.

Poikilothermic Animals as a Previously Unrecognized Source of Fecal Indicator Bacteria in a Backwater Ecosystem of a Large River.

Quantitative information regarding the presence of Escherichia coli, intestinal enterococci, and Clostridium perfringens in poikilotherms is notably scarce. Therefore, this study was designed to allow a systematic comparison of the occurrence of these standard fecal indicator bacteria (SFIB) in the excreta of wild homeothermic (ruminants, boars, carnivores, and birds) and poikilothermic (earthworms, gastropods, frogs, and fish) animals inhabiting an alluvial backwater area in eastern Austria. With the exception of earthworms, the average concentrations of E. coli and enterococci in the excreta of poikilotherms were equal to or only slightly lower than those observed in homeothermic excreta and were 1 to 4 orders of magnitude higher than the levels observed in the ambient soils and sediments. Enterococci reached extraordinarily high concentrations in gastropods. Additional estimates of the daily excreted SFIB (E. coli and enterococcus) loads (DESL) further supported the importance of poikilotherms as potential pollution sources. The newly established DESL metric also allowed comparison to the standing stock of SFIB in the sediment and soil of the investigated area. In agreement with its biological characteristics, the highest concentrations of C. perfringens were observed in carnivores. In conclusion, the long-standing hypothesis that only humans and homeothermic animals are primary sources of SFIB is challenged by the results of this study. It may be necessary to extend the fecal indicator concept by additionally considering poikilotherms as potential important primary habitats of SFIB. Further studies in other geographical areas are needed to evaluate the general significance of our results. We hypothesize that the importance of poikilotherms as sources of SFIB is strongly correlated with the ambient temperature and would therefore be of increased significance in subtropical and tropical habitats and water resources.IMPORTANCE The current fecal indicator concept is based on the assumption that the standard fecal indicator bacteria (SFIB) Escherichia coli, intestinal enterococci, and Clostridium perfringens multiply significantly only in the guts of humans and other homeothermic animals and can therefore indicate fecal pollution and the potential presence of pathogens from those groups. The findings of the present study showed that SFIB can also occur in high concentrations in poikilothermic animals (i.e., animals with body temperatures that vary with the ambient environmental temperature, such as fish, frogs, and snails) in an alluvial backwater area in a temperate region, indicating that a reconsideration of this long-standing indicator paradigm is needed. This study suggests that poikilotherms must be considered to be potential primary sources of SFIB in future studies.

Determination of wild animal sources of fecal indicator bacteria by microbial source tracking (MST) influences regulatory decisions

Fecal indicator bacteria (FIB) are used to assess fecal pollution levels in surface water and are among the criteria used by regulatory agencies to determine water body impairment status. While FIB provide no information about pollution source, microbial source tracking (MST) does, which contributes to more direct and cost effective remediation efforts. We studied a watershed in Florida managed for wildlife conservation that historically exceeded the state regulatory guideline for fecal coliforms. We measured fecal coliforms, enterococci, a marker gene for avian feces (GFD), and a marker gene for human-associated Bacteroides (HF183) in sediment, vegetation, and water samples collected monthly from six sites over two years to: 1) assess the influence of site, temporal factors, and habitat (sediment, vegetation, and water) on FIB and MST marker concentrations, 2) test for correlations among FIB and MST markers, and 3) determine if avian feces and/or human sewage contributed to FIB levels. Sediment and vegetation had significantly higher concentrations of FIB and GFD compared to water and thus may serve as microbial reservoirs, providing unreliable indications of recent contamination. HF183 concentrations were greatest in water samples but were generally near the assay limit of detection. HF183-positive results were attributed to white-tailed deer (Odocoileus virginianus) feces, which provided a false indication of human sewage in this water body. FIB and GFD were positively correlated while FIB and HF183 were negatively correlated. We demonstrated that birds, not sewage, were the main source of FIB, thus avoiding implementation of a total maximum daily load program (TMDL). Our results demonstrate that the concomitant use of FIB and MST can improve decision-making and provide direction when water bodies are impaired, and provides a strategy for natural source exclusion in water bodies impacted by wild animal feces.

Evaluation of the dry and wet weather recreational health risks in a semi-enclosed marine embayment in Southern California

For many coastal regions around the world, recreational beach water quality is assessed using fecal indicator bacteria (FIB). However, the utility of FIB as indicators of recreational water illness (RWI) risk has been questioned, particularly in coastal settings with no obvious sources of human sewage. In this study we employed a source-apportionment quantitative microbial risk assessment (SA-QMRA) to assess RWI risk at a popular semi-enclosed recreational beach in Southern California (Baby Beach, City of Dana Point) with no obvious point sources of human sewage. Our SA-QMRA results suggest that, during dry weather, the median RWI risk at this beach is below the U.S. EPA recreational water quality criteria (RWQC) of 36 illness cases per 1000 bathers. During wet weather, the median RWI risk predicted by SA-QMRA depends on the assumed level of human waste associated with stormwater; the RWI risk is below the EPA RWQC illness risk benchmark 100% of the time provided that <2% of the FIB in stormwater are of human origin. However, these QMRA outcomes contrast strongly with the EPA RWQC for 30-day geometric mean of enterococci bacteria. Our results suggest that SA-QMRA is a useful framework for estimating robust RWI risk that takes into account local information about possible human and non-human sources of FIB.

Microbial source tracking in shellfish harvesting waters in the Gulf of Nicoya, Costa Rica

Current microbial water quality monitoring is generally limited to culture-based measurements of fecal indicator bacteria (FIB). Given the many possible sources of fecal pollution within a watershed and extra-intestinal FIB reservoirs, it is important to determine source(s) of fecal pollution as a means to improve water quality and protect public health. The principal objective of this investigation was to characterize the microbial water quality of shellfish harvesting areas in the Gulf of Nicoya, Costa Rica during 2015. In order to achieve this objective, the specificity and sensitivity of 11 existing microbial source tracking (MST) PCR assays, associated with cows (BacCow), dogs (BacCan, DogBac), domestic wastewater (PMMoV), general avian (GFD), gulls (Gull2), horses (HorseBac, HoF), humans (HF183, HPyV), and pigs (PF), were evaluated using domestic wastewater and animal fecal samples collected from the region. The sensitivity of animal-associated assays ranged from 13 to 100%, while assay specificity ranged from 38 to 100%. The specificity of pepper mild mottle virus (PMMoV) and human polyomavirus (HPyV) was 100% for domestic wastewater, as compared to 94% specificity of the HF183 Bacteroidales marker. PMMoV was identified as a useful domestic wastewater-associated marker, with concentrations as high as 1.1 × 105 copies/ml and 100% sensitivity and specificity. Monthly surface water samples collected from four shellfish harvesting areas were analyzed using culture-based methods for Escherichia coli as well as molecular methods for FIB and a suite of MST markers, which were selected for their specificity in the region. While culturable E. coli results suggested possible fecal pollution during the monitoring period, the absence of human/domestic wastewater-associated markers and low FIB concentrations determined using molecular methods indicated sufficient microbial water quality for shellfish harvesting. This is the first study to our knowledge to test the performance of MST markers in Costa Rica as well as in Central America. Given the lack of wastewater treatment and the presence of secondary sources of FIB, this study highlights the importance of an MST toolbox approach to characterize water quality in tropical regions. Furthermore, it confirms and extends the geographic range of PMMoV as an effective tool for monitoring domestic wastewater pollution.

Microbial source tracking in impaired watersheds using PhyloChip and machine-learning classification

Sources of fecal indicator bacteria are difficult to identify in watersheds that are impacted by a variety of non-point sources. We developed a molecular source tracking test using the PhyloChip microarray that detects and distinguishes fecal bacteria from humans, birds, ruminants, horses, pigs and dogs with a single test. The multiplexed assay targets 9001 different 25-mer fragments of 16S rRNA genes that are common to the bacterial community of each source type. Both random forests and SourceTracker were tested as discrimination tools, with SourceTracker classification producing superior specificity and sensitivity for all source types. Validation with 12 different mammalian sources in mixtures found 100% correct identification of the dominant source and 84–100% specificity. The test was applied to identify sources of fecal indicator bacteria in the Russian River watershed in California. We found widespread contamination by human sources during the wet season proximal to settlements with antiquated septic infrastructure and during the dry season at beaches during intense recreational activity. The test was more sensitive than common fecal indicator tests that failed to identify potential risks at these sites. Conversely, upstream beaches and numerous creeks with less reliance on onsite wastewater treatment contained no fecal signal from humans or other animals; however these waters did contain high counts of fecal indicator bacteria after rain. Microbial community analysis revealed that increased E. coli and enterococci at these locations did not co-occur with common fecal bacteria, but rather co-varied with copiotrophic bacteria that are common in freshwaters with high nutrient and carbon loading, suggesting runoff likely promoted the growth of environmental strains of E. coli and enterococci. These results indicate that machine-learning classification of PhyloChip microarray data can outperform conventional single marker tests that are used to assess health risks, and is an effective tool for distinguishing numerous fecal and environmental sources of pathogen indicators.

Release of Escherichia coli from Foreshore Sand and Pore Water during Intensified Wave Conditions at a Recreational Beach.

Foreshore beach sands and pore water may act as a reservoir and nonpoint source of fecal indicator bacteria (FIB) to surface waters. This paper presents data collected at a fine sand beach on Lake Huron, Canada over three field events. The data show that foreshore sand erosion as wave height increases results in elevated Escherichia coli concentrations in surface water, as well as depletion of E. coli from the foreshore sand and pore water. E. coli initially attached to foreshore sand rather than initially residing in the pore water was found to be the main contributor to elevated surface water concentrations. Surface water E. coli concentrations were a function of not only wave height (and associated sand erosion) but also the time elapsed since a preceding period of high wave intensity. This finding is important for statistical regression models used to predict beach advisories. While calculations suggest that foreshore sand erosion may be the dominant mechanism for releasing E. coli to surface water during intensified wave conditions at a fine sand beach, comparative characterization of the E. coli distribution at a coarse sand-cobble beach suggests that interstitial pore water flow and discharge may be more important for coarser sand beaches.

Fecal Indicator Bacteria Entrainment from Streambed to Water Column: Transport by Unsteady Flow over a Sand Bed

Storms cause a substantial increase in the fecal indicator bacteria (FIB) concentrations in stream water as a result of FIB-laden runoff and the release of FIB from stream sediments. Previous work has emphasized the association between FIB and bed sediments finer than sand. The objectives of this work were to elucidate the effect of various velocities on the entrainment of bed-dwelling coliforms in sand-bed streams and to refine methodologies for quantifying sandy streambeds as sources of FIB. Pump-induced hydrographs were created using a stainless steel nonrecirculating flume. Experiments consisted of simulating four storm hydrographs and collecting water samples upstream and downstream of a sand bed at selected intervals. Bed sediment samples were collected before and after each event. The highest concentrations of total coliform and suspended sediments generally occurred in the downstream samples during the rising limb of the hydrographs as a result of entrainment of coliforms and sand from the bed to the water column. There was a first flush effect in the system, as the upper layer of sand was influenced by a rapidly increasing velocity at ∼0.2 m s. Coliforms downstream of the sand bed increased rapidly as velocity exceeded this threshold but then declined even as velocity and discharge continued to increase. This likely reflects the depletion of coliforms as the more densely populated sediment layer was flushed out. There is evidence that streams with sand beds harbor enough FIB that development of total maximum daily loads (TMDLs) should include consideration of them as a source.

Monitoring and predicting the fecal indicator bacteria concentrations from agricultural, mixed land use and urban stormwater runoff

While the urban runoff are increasingly being studied as a source of fecal indicator bacteria (FIB), less is known about the occurrence of FIB in watershed with mixed land use and ongoing land use and land cover (LULC) change. In this study, Escherichia coli (EC) and fecal streptococcus (FS) were monitored from 2012 to 2013 in agricultural, mixed and urban LULC and analyzed according to the most probable number (MPN). Pearson correlation was used to determine the relationship between FIB and environmental parameters (physicochemical and hydrometeorological). Multiple linear regressions (MLR) were used to identify the significant parameters that affect the FIB concentrations and to predict the response of FIB in LULC change. Overall, the FIB concentrations were higher in urban LULC (EC=3.33–7.39; FS=3.30–7.36log10MPN/100mL) possibly because of runoff from commercial market and 100% impervious cover (IC). Also, during early-summer season; this reflects a greater persistence and growth rate of FIB in a warmer environment. During intra-event, however, the FIB concentrations varied according to site condition. Anthropogenic activities and IC influenced the correlation between the FIB concentrations and environmental parameters. Stormwater temperature (TEMP), turbidity, and TSS positively correlated with the FIB concentrations (p>0.01), since IC increased, implying an accumulation of bacterial sources in urban activities. TEMP, BOD5, turbidity, TSS, and antecedent dry days (ADD) were the most significant explanatory variables for FIB as determined in MLR, possibly because they promoted the FIB growth and survival. The model confirmed the FIB concentrations: EC (R2=0.71–0.85; NSE=0.72–0.86) and FS (R2=0.65–0.83; NSE=0.66–0.84) are predicted to increase due to urbanization. Therefore, these findings will help in stormwater monitoring strategies, designing the best management practice for FIB removal and as input data for stormwater models.

U.S. Recreational Water Quality Criteria: A Vision for the Future.

This manuscript evaluates the U.S. Recreational Water Quality Criteria (RWQC) of 2012, based upon discussions during a conference held 11–13 March 2013, in Honolulu, Hawaii. The RWQC of 2012 did not meet expectations among the research community because key recommended studies were not completed, new data to assess risks to bathers exposed to non-point sources of fecal indicator bacteria (FIB) were not developed, and the 2012 RWQC did not show marked improvements in strategies for assessing health risks for bathers using all types of recreational waters. The development of the 2012 RWQC was limited in scope because the epidemiologic studies at beach sites were restricted to beaches with point sources of pollution and water samples were monitored for only enterococci. The vision for the future is development of effective RWQC guidelines based on epidemiologic and quantitative microbial risk assessment (QMRA) studies for sewage specific markers, as well as human enteric pathogens so that health risks for bathers at all recreational waters can be determined. The 2012 RWQC introduced a program for states and tribes to develop site-specific water quality criteria, and in theory this approach can be used to address the limitations associated with the measurements of the traditional FIB.

Human health risk implications of multiple sources of faecal indicator bacteria in a recreational waterbody

We simulate the influence of multiple sources of enterococci (ENT) as faecal indicator bacteria (FIB) in recreational water bodies on potential human health risk by considering waters impacted by human and animal sources, human and non-pathogenic sources, and animal and non-pathogenic sources. We illustrate that risks vary with the proportion of culturable ENT in water bodies derived from these sources and estimate corresponding ENT densities that yield the same level of health protection that the recreational water quality criteria in the United States seeks (benchmark risk). The benchmark risk is based on epidemiological studies conducted in water bodies predominantly impacted by human faecal sources. The key result is that the risks from mixed sources are driven predominantly by the proportion of the contamination source with the greatest ability to cause human infection (potency), not necessarily the greatest source(s) of FIB. Predicted risks from exposures to mixtures comprised of approximately 30% ENT from human sources were up to 50% lower than the risks expected from purely human sources when contamination is recent and ENT levels are at the current water quality criteria levels (35 CFU 100 mL-1). For human/non-pathogenic, human/gull, human/pig, and human/chicken faecal mixtures with relatively low human contribution, the predicted culturable enterococci densities that correspond to the benchmark risk are substantially greater than the current water quality criteria values. These findings are important because they highlight the potential applicability of site specific water quality criteria for waters that are predominantly un-impacted by human sources.

Impacts of a Poultry Processing Plant on the Diversity of Escherichia coli Populations and Transferability of Tetracycline Resistance Genes in an Urban Stream in South Carolina

Poultry feed is often supplemented with low dosages of antibiotic to promote growth, making farms and animal processing facilities potential point sources of antibiotic-resistant fecal bacteria to aquatic ecosystems. In 2010 and 2011, we detected high concentrations of fecal indicator bacteria (FIB) in effluent released from a poultry processing plant into a headwater stream in Greenville, South Carolina. The FIB pollution became undetectable in 2012 with the plant under new management. To determine the plant’s impacts on the stream, we compared the genetic variations of Escherichia coli populations from upstream and downstream of the plant and from reference streams in the same watershed by classifying each isolate into an E. coli reference collection (ECOR) phylogenetic group. For tetracycline-resistant E. coli isolates, we analyzed the resistance genes, minimum inhibitory concentrations (MICs), gene transferability, and plasmid incompatibility groups (Inc). Distributions of ECOR groups upstream and downstream of the plant differed significantly in 2011 but not in 2012. The resistance genes tet(A) and tet(B) were prevalent, with tet(A) more likely to be found on the promiscuous IncP plasmid. A higher percentage of isolates having both tet(A) and tet(B) was found downstream in 2011 than in 2012. Dual-gene isolates did not have higher MICs than single-gene isolates but were more likely to transfer tet(A) on IncP. We propose that the processing plant acted not only as a point source of FIB but also as a factor influencing gene transferability. Additionally, given the results from 2012, the FIB impacts of the processing plant appeared to be reversible.

Fecal Indicator Bacteria Levels Do Not Correspond with Incidence of Human-Associated HF183 Bacteroides 16S rRNA Genetic Marker in Two Urban Southern California Watersheds

The variability of levels of fecal indicator bacteria (FIB) and a human-associated genetic marker (HF183) during wet and dry weather conditions was investigated at two urban coastal watersheds in Southern California: Santa Monica Canyon channel (SMC) and Ventura Harbor, Keys, and Marina. Seventy-eight to 86 % of the samples collected from SMC sites exceeded standard water quality standards for FIB (n = 59 to 76). At SMC, HF183 was present in 58 % of the samples (n = 78) and was detected at least once at every sample site. No individual site at SMC appeared as a hotspot for the measured indicators, pointing to a likely chronic issue stemming from urban runoff in wet and dry weather. In Ventura, the Arundell Barranca, which drains into Ventura Harbor and Marina, was a source of FIB, and HF183 was most frequently detected off of a dock in the Marina. Rainfall significantly increased FIB levels at both SMC and Ventura; only at Ventura did HF183 detection increase with wet weather. Sample locations that were high in FIB were geographically distinct from the sites that were high in HF183 in Ventura, which supports the importance of measuring host-associated parameters along with FIB in chronically impaired watersheds to guide water quality managers in pollution remediation efforts.

Impacts of Beach Wrack Removal via Grooming on Surf Zone Water Quality

Fecal indicator bacteria (FIB) are used to assess the microbial water quality of recreational waters. Increasingly, nonfecal sources of FIB have been implicated as causes of poor microbial water quality in the coastal environment. These sources are challenging to quantify and difficult to remediate. The present study investigates one nonfecal FIB source, beach wrack (decaying aquatic plants), and its impacts on water quality along the Central California coast. The prevalence of FIB on wrack was studied using a multibeach survey, collecting wrack throughout Central California. The impacts of beach grooming, to remove wrack, were investigated at Cowell Beach in Santa Cruz, California using a long-term survey (two summers, one with and one without grooming) and a 48 h survey during the first ever intensive grooming event. FIB were prevalent on wrack but highly variable spatially and temporally along the nine beaches sampled in Central California. Beach grooming was generally associated with either no change or a slight increase in coastal FIB concentrations and increases in surf zone turbidity and silicate, phosphate, and dissolved inorganic nitrogen concentrations. The findings suggest that beach grooming for wrack removal is not justified as a microbial pollution remediation strategy.

Microbial investigations of water, sediment, and algal mats in the mixed use watershed of Saginaw Bay, Michigan

Beach monitoring often includes testing for a single fecal indicator organism in the swimmable waters. Here, sediment, algae mat, shallow water, and deep water samples collected from four Saginaw Bay (Michigan, USA) beaches were tested for multiple fecal indicator organisms (Escherichia coli, enterococci, Clostridium perfringens, F+amp coliphage, and CN-13 coliphage) and molecular markers (human and bovine Bacteroides and enterococci surface protein) to determine the occurrence and sources of fecal indicator bacteria across beachscapes and characterize the environmental parameters which influence microbial water quality. Results show algae mats and sediment had higher levels of bacteria compared to surrounding water column. Higher concentrations of fecal indicators in shallow waters compared to deep water were attributed in part to sediment and algae bound bacteria and potential regrowth. Fecal indicator organisms were primarily influenced by wind, waves, and precipitation and partially identified as human specific using the enterococci surface protein gene. This project suggests the potential for sediment and algal mats to act as non-point sources of pollution in the nearshore zone. Future beach protection measures should focus on shallow water monitoring of multiple fecal indicators and beach grooming during calm morning hours.