Microbial Concentrations in Sand and their Effect on Beach Water in Door County,Wisconsin

The seasonal variations and patterns of Escherichia coli in Wisconsin's coastal waters have been closely studied in recent years due to increased beach monitoring activities. Patterns of distribution of the indicator organism, E. coli, in the sand at these beaches are now being investigated as a source of E. coli to adjacent beach water. This project investigates the concentrations of E. coli in beach sand, and the relationship between these sand-microbe concentrations and concentrations of microbes in the corresponding beach water. Weekly sampling of upshore, swash, and submerged sand at six beaches provided numbers of the indicator bacteria in each beach's sand substrate for two consecutive summers. Overall concentrations of E. coli were highest in the swash sand of the beach, with the highest numbers seen in the summer months and lowest numbers in the winter months. Each location had very different concentrations of E. coli in the beach sand from 1,800 CFU/100 g to 21,670 CFU/100 g sand. Each location had a very different relationship between the indicator organism found in the beach sand and that found in the beach water. These data suggest that sand may be a reservoir for E. coli at some locations, and another source of contamination that should be considered in beach monitoring programs. However, elevated levels of E. coli in beach sand were not universal and varied greatly from location to location.     

Influence of Nearshore Water Dynamics and Pollution Sources on Beach Monitoring Outcomes at Two Adjacent Lake Michigan Beaches

Beach closings are a growing concern in coastal regions because of serious public health and economic ramifications. Two beach sites separated by 150 m of shoreline on Lake Michigan were monitored in the summer of 2003 and 2004 for E. coli densities to evaluate the potential outcome of relocating an existing beach to a site immediately to the south. Under identical weather conditions, there was a large disparity between the two sites for 25 of the 39 days tested, where E. coli levels at the existing beach were at least twice as high as those at the proposed beach. Following rainfall, E. coli levels at the existing beach increased up to 100-fold to levels as high as 4,500 CFU/100 mL, whereas only a 10-fold increase in levels was observed at the proposed beach site. Water exchange in the beach areas was predominantly from wind driven currents rather than dilution, and longshore current speed at the proposed beach was calculated to be twice that of the existing beach. Stormwater and combined sewer overflow (CSO) discharged from two closely spaced outfalls approximately 0.5 km north of the existing beach was found to have E. coli levels above the EPA recommended limit of 235 CFU/100 mL for recreational waters. However, this input did not appear to be a major influence on beach monitoring results. In some cases, E. coli levels at the beach did not exceed 235 E. coli/100 mL during a CSO. Defining the sources and spatial range of pollution inputs would allow beach monitoring results to be interpreted in a more meaningful context, which may lead to the formation of effective management strategies.     

Escherichia coli (E. coli) distribution in the Lake Malawi nearshore zone

Residents along the shoreline of Lake Malawi depend on nearshore water for drinking, cooking, and bathing. Despite the importance of clean nearshore waters to public health, we are aware of no published studies of shoreline water quality in the lake. To address this gap, we explore seasonal and temporal trends of the fecal indicator bacteria Escherichia coli (E. coli) in nearshore water and sand. E. coli concentrations in sand ranged from 0 to 17,600 colony forming units (CFU)/100?ml, and in water concentrations ranged from 0 to 21,200?CFU/100?ml. Fifty-three percent of water samples exceeded the U.S. Environmental Protection Agency Recreational Water Quality Criteria of 126?CFU/100?ml, and 90% exceeded the World Health Organization drinking water standard of 0?CFU/100?ml. Distance from shore was the variable most predictive of E. coli concentration, with the level of beach use also playing a significant role. At 15?m from the shore, E. coli concentrations dropped to between 0.3% and 17% of shoreline values. Results suggest that the collection of water at distances >15?m from the beach could substantially decrease exposure to fecal bacteria. Further studies are needed to identify sources of fecal pollution and to determine the utility of E. coli as a predictor of the potential for waterborne disease.     

Escherichia coli toxin and attachment genes in sand at Great Lakes recreational beaches

The United States Environmental Protection Agency recommends density thresholds for the fecal indicator organism Escherichia coli in order to ensure the safety of recreational waters. A number of studies published over the past ten years indicate that E. coli is encountered frequently in sand at recreational beaches. While a majority of the sand-associated E. coli may be commensal or environmental strains, the potential for pathogenic strains of E. coli to be present exists. Therefore, the aim of this study was to assess the presence of attachment and virulence genes associated with enteropathogenic and enterohemorrhagic strains of E. coli (EPEC and EHEC) in populations of E. coli recovered from swash zone sand from seven recreational beaches along Lake Huron and Lake St. Clair in eastern Michigan, USA. Genes coding for attachment proteins in EPEC and EHEC were very prevalent in sand E. coli, but genes coding for toxin genes were uncommon. The paucity of genes associated with E. coli toxins suggests that the EPEC and EHEC pathotypes are not common in sand; however, the high prevalence of genes associated with attachment in E. coli pathotypes suggests that these genes are being retained within the beach sand E. coli population.     

Fecal indicator organism density in beach sands: Impact of sediment grain size,uniformity, and hydrologic factors on surface water loading

Fecal loading to beach sands and subsequent transport to surface water may result in the degradation of surface water quality. To better understand the relationship between Escherichia coli in sands, beach hydrology, and recreational water quality, we collected surface water, groundwater, and sand samples from three Lake Michigan beaches with varying substrates (fine sand to pebbles, July 2005–June 2006). Sediment cores collected within transects perpendicular to and at fixed distances from the shoreline (0 m, 10 m, 20 m) and surface water samples collected at a depth of 1 m were analyzed for E. coli. Grain size analysis was performed on duplicate core samples to assess the relationship between E. coli density and mean grain size and uniformity. Groundwater samples, collected from shallow drive-point piezometers within the test area, were also analyzed for E. coli. E. coli density in beach sands differed significantly with distance from shore with the highest density occurring at the berm crest (0 m). Mean grain size and uniformity accounted for variation in E. coli density with fine sand of uniform distribution having the highest content. E. coli density in surface water was correlated to E. coli density in beach sand samples at the berm crest. E. coli in groundwater was < 10 to 579 MPN/100 ml (2005); none was detected in 2006. Management interventions, including altered beach grooming practices and slope assessments, may be effective in reducing E. coli content at beaches comprised of fine sands of uniform grain size, hence reducing water quality advisories.     

The establishment of the nuisance cyanobacteria Lyngbya wollei in Lake St. Clair and its potential to harbor fecal indicator bacteria

Lyngbya wollei is a filamentous cyanobacterium which forms large nuisance mats and has infested eastern and southeastern U.S. Lakes and reservoirs for over 100 years. Lyngbya was recently identified in the Great Lakes system in the St. Lawrence River, and Western Lake Erie. Here we report on large deposits of L. wollei washing onshore at a popular recreational beach in Lake Saint Clair, part of the Great Lakes system. The amount of L. wollei deposited on shore was quantified and evaluated for the presence of fecal indicator bacteria (FIB). High concentrations of Escherichia coli, enterococci and Clostridium perfringens were found in the L. wollei in nearshore waters. The densities of E. coli (MPN), enterococci (MPN) and C. perfringens (CFU) attached to L. wollei averaged 3.5, 3.2 and 3.2 log/g, respectively. In contrast, nearshore waters contained nearly 10 times less FIB, averaging 2.6, 2.4 and 2.6 log/100 ml of E. coli (MPN), enterococci (MPN) and C. perfringens (CFU), respectively. DNA fingerprint analysis was used to examine the population structure of E. coli isolates obtained from L. wollei mats. The L. wollei-borne E. coli strains were genetically diverse, suggesting a causal relationship between E. coli and L. wollei. Results from this study indicate that in addition to the macroalga such as Cladophora, cyanobacteria like L. wollei also harbor FIB, potentially impacting water quality and human health in the Great Lakes.     

Effect of hydrological and geophysical factors on formation of standing water and FIB reservoirs at a Lake Michigan beach

Water quality impairment of Great Lakes beaches is caused by fecal pollution from point and nonpoint sources. Erosion due to wind or wave action, invasive vegetation and chronically wet, flooded or standing water are conditions that can magnify water quality problems at beaches. We investigated the hydrological and geophysical characteristics of the Bradford Beach on Lake Michigan (Milwaukee, WI) and the linkage between standing water and persistent contamination by fecal indicator bacteria (FIB). Our study showed that there is a positive correlation between high concentrations of Escherichia coli (E. coli) in sand and high moisture content caused by standing water. The main factor associated with the formation of standing water was rainfall. There were also notable differences in standing water and/or wet sand conditions in the northern and southern parts of the beach. These differences could be accounted for by differences in ground water elevations and beach erosion and accretion patterns. Other important physical features of the beach were the presence of rain gardens and mean grain diameter (d₅₀). Rain gardens above the beach face that capture runoff contributed to transient increases in the water table, facilitating standing water formation. Standing water, stormwater runoff infiltrating through the sand and into groundwater as well as wave run up that delivered contaminated surface water to the back beach area were of health concern following heavy rainfall events. The outcomes of this study will likely be useful to beach managers investigating mechanisms/sources of fecal indicator bacteria loading and potential mitigative approaches.     

Influences on Bythotrephes longimanus life-history characteristics in the Great Lakes

We compared Bythotrephes population demographics and dynamics to predator (planktivorous fish) and prey (small-bodied crustacean zooplankton) densities at a site sampled through the growing season in Lakes Michigan, Huron, and Erie. Although seasonal average densities of Bythotrephes were similar across lakes (222/m² Erie, 247/m² Huron, 162/m² Michigan), temporal trends in abundance differed among lakes. In central Lake Erie where Bythotrephes' prey assemblage was dominated by small individuals (60%), where planktivorous fish densities were high (14,317/ha), and where a shallow water column limited availability of a deepwater refuge, the Bythotrephes population was characterized by a small mean body size, large broods with small neonates, allocation of length increases mainly to the spine rather than to the body, and a late summer population decline. By contrast, in Lake Michigan where Bythotrephes' prey assemblage was dominated by large individuals (72%) and planktivorous fish densities were lower (5052/ha), the Bythotrephes population was characterized by a large mean body size (i.e., 37–55% higher than in Erie), small broods with large neonates, nearly all growth in body length occurring between instars 1 and 2, and population persistence into fall. Life-history characteristics in Lake Huron tended to be intermediate to those found in Lakes Michigan and Erie, reflecting lower overall prey and predator densities (1224/ha) relative to the other lakes. Because plasticity in life history can affect interactions with other species, our findings point to the need to understand life-history variation among Great Lakes populations to improve our ability to model the dynamics of these ecosystems.     

Sources and Sinks of Escherichia coli in Benthic and Pelagic Fish

Escherichia coli and fecal coliform bacteria were isolated from five benthic and four pelagic fish species to determine their role in the fecal contamination of recreational waters. All fish were collected during fall 2006 from Southworth Marsh in the Duluth-Superior Harbor, a public beach that is commonly posted to minimize water contact due to high E. coli levels. Although fecal coliform bacteria were isolated from each fish species, they were only isolated from 66% and 72% of the individual benthic and pelagic fish, respectively. While 42% of the fecal coliforms from benthic fish were E. coli, only 4% of these bacteria from pelagic fish were E. coli. Cluster analysis showed different fish species harbored identical strains of E. coli and some fish contained multiple E. coli strains. The potential source for 65% of the E. coli isolates obtained from fish were identified by using the HFERP DNA fingerprinting method and libraries of E. coli DNA fingerprints from warm-blooded animals and environmental isolates collected in the area. The E. coli strains whose source could be identified were most similar to strains isolated from sediments, Canada geese, mallard ducks, and wastewater. None of the fish E. coli had DNA fingerprints matching those from any water or beach sand isolates. Although our results demonstrate that benthic fish contain E. coli, it may be more appropriate to consider these fish as a vector of E. coli from other sources, rather than a new source of E. coli contamination in aquatic environments.     

Trends in Diporeia populations across the Laurentian Great Lakes, 1997-2009

Benthic communities in the Laurentian Great Lakes have been in a state of flux since the arrival of dreissenid mussels, with the most dramatic changes occurring in population densities of the amphipod Diporeia. In response, the US EPA initiated an annual benthic macroinvertebrate monitoring program on all five Great Lakes in 1997. Although historically the dominant benthic invertebrate in all the lakes, no Diporeia have been found in Lake Erie during the first 13 years of our study, confirming that Diporeia is now effectively absent from that lake. Populations have almost entirely disappeared from our shallow (< 90 m) sites in lakes Ontario, Huron, and Michigan. In Lake Ontario, three of our four deep (> 90 m) sites still supported Diporeia populations in 2009, with densities at those sites ranging between 96 and 198/m². In Lake Michigan, populations were still found at six of our seven deep sites in 2009, with densities ranging from 57 to 1409/m². Densities of Diporeia in 2009 at the four deep sites in Lake Huron were somewhat lower than those in Lake Michigan, ranging from 191 to 720/m². Interannual changes in population size in Lake Huron and Lake Michigan have shown a degree of synchrony across most sites, with periods of rapid decline (1997-2000, 2003-2004) alternating with periods of little change or even increase (2001-2002, 2005-2009). There has been no evidence of directional trends at any sites in Lake Superior, although substantial interannual variability was seen.     

Ground-penetrating radar stratigraphy and depositional model for evolving Late Holocene aeolian dunes on the Lake Huron coast,Ontario

One of the largest (36 km²) Late Holocene systems anywhere in Ontario lies in Pinery Provincial Park on the southeast coast of Lake Huron and postdates a 12‐km‐long beach barrier system left by Lake Nipissing some 5000 years ago. Dunes lie parallel to the lake shoreline, oblique to the dominant west–northwest wind. Linear dunes in the north of the field regardless of age are stable and of moderate height (< 10 m) having grown in situ from foredunes on emergent beach ridges. Southwards however, the same dunes evolve into wider, higher (up to 20 m) parabolic forms with large blow outs. This change in form from north to south appears to have been a persistent evolutionary trend over the past 5000 years. Some 5 km of high resolution radar profiles identifies the changing internal stratigraphy of dunes as they evolve in shape. Linear dunes are composed of a ‘vertical aggradation sequence’ (VAS) that records initial formation of a foredune on top of shore-parallel beach ridges, and upwards growth of the dune by sand trapped by vegetation. Southwards over some 12 km, dunes grow in height and assume a parabolic form expressed on radar profiles by a lowermost VAS overlain by cross-bedded sand comprising a landward accretion sequence (LAS) recording landward migration. A depositional model relates the change in dune shape and stratigraphy to southward increasing sand supply within a large persistent littoral cell in Lake Huron.     

Ensuring water security by utilizing roof-harvested rainwater and lake water treated with a low-cost integrated adsorption-filtration system

Drinking water is supplied through a centralized water supply system and may not be accessed by communities in rural areas of Malaysia. This study investigated the performance of a low-cost, self-prepared combined activated carbon and sand filtration (CACSF) system for roof-harvested rainwater and lake water for potable use. Activated carbon was self-prepared using locally sourced coconut shell and was activated using commonly available salt rather than a high-tech procedure that requires a chemical reagent. The filtration chamber was comprised of local, readily available sand. The experiments were conducted with varying antecedent dry intervals (ADIs) of up to 15 d and lake water with varying initial chemical oxygen demand (COD) concentration. The CACSF system managed to produce effluents complying with the drinking water standards for the parameters pH, dissolved oxygen (DO), biochemical oxygen demand (BOD₅), COD, total suspended solids (TSS), and ammonia nitrogen (NH₃-N). The CACSF system successfully decreased the population of Escherichia coli (E. coli) in the influents to less than 30 CFU/mL. Samples with a higher population of E. coli (that is, greater than 30 CFU/mL) did not show 100% removal. The system also showed high potential as an alternative for treated drinking water for roof-harvested rainwater and class II lake water.     

Distribution and Fate of Escherichia coli in Lake Michigan Following Contamination with Urban Stormwater and Combined Sewer Overflows

Escherichia coli distribution and persistence in nearshore Lake Michigan were assessed following heavy rains and sanitary sewer overflow (SSO) and combined sewer overflow (CSO) events over a 5-year period, including an 18-day period following 25.4 cm of rainfall in which intensive studies were conducted following multiple CSO and SSO events. E. coli levels in the Milwaukee estuary and harbor following SSO and CSO events ranged from 10⁴ to nearly 10⁵ CFU/100 mL, which were significantly higher (p ≤ 0.05) than levels following rainfall alone. Sites outside of the breakwall but within the contamination plume (e.g., within 2 km of the harbor) were an order of magnitude lower. Locations 2–5 km from the harbor ranged from below detection limits, of < 1 to 5 CFU/100 mL. E. coli levels corrected for dilution based on specific conductivity measurements were lower than what would be expected for loss due to dilution alone, suggesting a combination of die-off and dilution, were responsible for the rapid disappearance of these organisms outside of the harbor. E. coli and fecal coliforms measured concurrently demonstrated that fecal coliforms could be recovered longer than E. coli in the open waters of the lake. E. coli isolated directly from sewage treatment plant influent were found to have a marked increase in antibiotic resistance traits for ten antibiotics commonly used in the human population compared with isolates from two animal sources of fecal pollution. However, E. coli obtained from sewage impacted water (n = 2,513) and from stormwater impacted water (n = 1,465) collected the previous year when there were no sewage overflows, were found to have no significant difference (p < 0.05) in the frequency of resistance when comparing the two conditions. E. coli survival characteristics and population dynamics are most likely influenced by multiple factors in complex systems such as the watershed/estuarine/lake environments of the Great Lakes.     

Impacts of manure management practices on stream microbial loading into Conesus Lake,NY

The microbiology of stream water has a seasonal component that results from both biogeochemical and anthropogenic processes. Analysis of nonevent conditions in streams entering Conesus Lake, NY (USA), indicated that total coliform, Escherichia coli, and Enterococcus spp. levels peak in the summer in all streams, independent of the agricultural use in the stream sub-watershed. Prior to implementation of management practices, E. coli in water draining Graywood Gully, a sub-watershed with 74% of the land in agriculture, reached as high as 2806 CFU/100 mL, exceeding the 235 CFU/100 mL EPA Designated Bathing Beach Standard (EPA-DBBS). In contrast, North McMillan Creek, a sub-watershed with < 13% of its land in agriculture, had E. coli maxima generally near or below the EPA-DBBS. Graywood Gully at times had a higher microbial loading than North McMillan Creek, a sub-watershed 48 times larger in surface area. Over a 5-year study period, there was a major decrease in bacterial loading during nonevent conditions at Graywood Gully, especially after manure management practices were implemented, while bacterial loading was constant or increased in streams draining three other sub-watersheds. E. coli levels dropped more than 10 fold to levels well below the EPA-DBBS while the yearly maximum for Enterococcus dropped by a factor 2.5. Similarly, exceedency curves for both E. coli and Enterococcus also showed improvement since there were fewer days during which minimum standards were exceeded. Even so, Graywood Gully at times continued to be a major contributor of E. coli to Conesus Lake. If wildlife represents a significant source of indicator bacteria to Graywood Gully as has been reported, stream remediation, management efforts and compliance criteria will need to be adjusted accordingly.     

Initial Colonization of the Zebra Mussel (Dreissena polymorpha) in Saginaw Bay,Lake Huron: Population Recruitment,Density, and Size Structure

The various life stages of the zebra mussel (Dreissena polymorpha) were examined during the initial years (1991–93) of the mussel's invasion into Saginaw Bay, Lake Huron. Yearly trends in densities of larvae, newly-settled juveniles, and adults were poorly related. Larval densities were lowest in 1991 and increased each year, but the number of settled juveniles was highest in 1991. Adults increased between 1991 and 1992 and then declined in 1993. Mean adult densities at sites with hard substrates were 11,700, 33,200, and 4,100/m² in each of the 3 years, respectively. Year-to-year variation at individual sites was high and likely a result of recruitment dynamics and spatial patchiness of available substrate. By 1993, densities on hard substrates were generally similar throughout the bay, but length-frequency distributions in the inner and outer bay were quite different. The 1991-cohort was not distinguishable in the inner bay in 1993 either because of poor growth or a limited life span, but this cohort was readily distinguishable in the outer bay. In addition, ash-free dry weight of a standard 15-mm mussel in the inner bay declined 65% between 1991 and 1993. Although food concentrations (chlorophyll and particulate organic carbon) declined to low levels in 1993 and both densities and soft-tissue weight of Dreissena declined, it is not clear whether populations in the bay have peaked and are now at equilibrium with the surrounding environment.     

Lipid Concentration and Size Variation of Bythotrephes (Cladocera: Cercopagidae) from Lakes Erie,Huron, and Michigan

Lipid concentrations of Bythotrephes cederstroemi were compared among three Great Lakes, Erie, Huron, and Michigan, in an effort to investigate the phenotypic plasticity in size displayed among the lakes. Four developmental stages were measured in Lakes Erie and Huron and two stages were studied in Lake Michigan. With a gravimetric extraction method, the total lipid concentration range (μg lipid μg dry weight⁻¹, expressed as percent) for Bythotrephes was estimated to be 10–19%. Statistically significant differences were found in lipid concentrations of Bythotrephes among lakes and developmental stages. Lake Erie had significantly higher lipid concentration values than Lake Huron for stages 2 through 4, and had similar values to Lake Michigan for the analyzed stages 1 and 4. The first instar had indistinguishable lipid concentrations among Lakes Erie, Huron,and Michigan. Even though animals from Lake Erie were significantly smaller, the data suggest that they were not less well nourished. We hypothesize that selective mortality imposed by visual predators on larger Bythotrephes and the lack of deep water refuges in Lake Erie has encouraged the smaller size of Bythotrephes found there in comparison to those found in Lakes Huron and Michigan.     

E. coli at Lake Superior Recreational Beaches

Increased usage of public beaches and heightened awareness of the need to monitor water for potential microbial contamination have led to passage of the U.S. Beaches Environmental Assessment and Coastal Health Act (BEACH Act) in 2000. This legislation calls for bacterial monitoring of recreational waters along the U.S. coastline, including the Great Lakes. The State of Wisconsin implemented this legislation in summer 2003, triggering extensive microbial monitoring of Lake Superior beaches. E. coli were measured at 27 beaches along Lake Superior, Wisconsin by defined substrate analysis. While E. coli concentrations were relatively low at these “cold water” beaches, monitoring did result in a few swimming advisories and beach closures (0.8% of total samples collected had E. coli concentrations that exceeded standards). Increasing water temperatures were not associated with increasing concentrations of bacterial contaminants. Location of sampling site and depth of water at the location where samples were taken did have an effect on detection of E. coli. Greater E. coli levels consistently were detected in shallower water and varied depending on the location of the sampling site horizontally across the beach. These findings support the notion that the concentration of E. coli in chest deep water may not be representative of E. coli concentrations in shallower water, closer to shore.     

Evaluation of Avian Waste and Bird Counts as Predicators of Escherichia coli Contamination at Door County,Wisconsin Beaches

Microbial source tracking (MST) has become a focus of some recreational beach monitoring programs. Suspected sources of contamination include human sewage, agricultural runoff, and feces from wildlife and domestic animals, depending on beach location. Waterfowl have been suggested as a primary source of fecal contamination at many beaches, but techniques to “prove” contaminating microbes are of avian origin are mostly unsubstantiated. Researchers often rely on bird counts to measure the impact of waterfowl on beach health. Since waterfowl populations at Door County, Wisconsin (USA) beaches are transitory, this study focused on enumeration of avian waste material along beach transects, rather than on once per day “snapshot” bird counts. Escherichia coli (E. coli) concentration in beach water was not correlated with avian waste counts at the ten beaches studied in 2004 or the 13 studied in 2005 (rural to semi-urban). Bird counts correlated with E. coli concentrations in beach water at 30% of the sample sites in 2004 and at only one site in 2005. During the 2004 swimming season avian waste counts correlated with bird counts at only one beach and there was no correlation in 2005. These results indicate that neither avian waste enumeration nor bird counts can successfully be used to predict microbial contamination of recreational water at selected Great Lakes beaches.     

Modelling of nearshore microbial water quality at confluence of a local tributary in Lake St. Clair

Microbial water quality, measured as Escherichia coli (E. coli) concentration, at beaches along the southern shore of Lake St. Clair in Canada, often exceeds public safety guidelines. Belle River, located near a public beach and a drinking water intake, is one of the several smaller tributaries of the lake whose contribution to nearshore microbial water quality is currently unknown. A flexible mesh 3D coupled TUFLOW-FV and Aquatic Ecodynamic (AED2+) model was used to simulate the hydrodynamics and microbial water quality in Lake St. Clair. A higher resolution nested model was developed within the lake-wide TUFLOW-FV model for better spatial and temporal resolution in the local region surrounding Belle River. Regular and up to a factor of four difference in predicted E. coli concentrations were observed with the nested and lake-wide models at the public beach next to Belle River, whereas the difference was marginal at the drinking water intake about a kilometre away from the shore. While the E. coli loading to Lake St. Clair from Belle River is considered negligible, >90% of the predicted daily E. coli concentration at the beach and > 50 % at the water intake were attributed to Belle River from amongst all watershed sources to Lake St. Clair considered in the model. The model results also show that the construction of a new 150 m jetty in 2018, replacing the older 25 m jetty separating Belle River from the public beach, is expected to significantly reduce E. coli concentrations observed at the beach.