Environmental health surveys of beaches and nearshore waters of the Great Lakes are invaluable to long-term management decisions. Human sewage contamination continues to affect beach water quality and leads to closures of popular recreational sites throughout the summer. Additionally, fish and bird carcasses can be found littering beaches during periodic outbreaks of botulism and offensive odors given off by excess quantities of decomposing algae discourage use of beaches by the public and may be harmful to humans. The USGS-GLSC has specific programs in place to assess the presence of beach pathogens (such as E. coli), nuisance algae, and botulism and is working to develop a better understanding of the physical and chemical factors that contribute to these outbreaks. Using the information gathered from monitoring efforts, predictive models can be created with the ability to forecast potential events. Through these projects, the UGSG-GLSC is striving to provide beach managers with reliable information so that necessary steps can be taken toward cleaner and healthier beach environments.
Beach Management Decisions
There is a decided need for a rapid means of characterizing microbiological water quality and for distinguishing sources of these natural indicator bacteria populations and associated human health risk. Currently, all Great Lakes coastal beaches (and marine beaches) are monitored for fecal indicator bacteria to determine when there is human fecal sewage contamination that may be harmful to human health. In recent years, numerous problems with the currently accepted indicator have been recognized. Notably, the analytical assay for E. coli requires 24 hours of culturing, a time frame lengthier than the rate of potentially significant changes in E. coli concentration in natural waters. A strong need for rapid assessment of microbiological water quality has developed.
Recent research has targeted several means of rapidly measuring water quality, among them faster analytical assays, a new indicator, and the use of empirical/statistical predictive models. Each possibility has advantages and disadvantages, many tied to specific situations at individual beaches. A clearer understanding of the application and implications of these rapid methods is needed so that beach managers can effectively manage their beaches to protect beachgoers. Different beaches may require different approaches to monitoring.
- Determine the predictability of rapid measurements of fecal indicator bacteria using hydrometeorological parameters, including nearshore hydrodynamics and water quality, plume dynamics, and weather conditions.
- Assess local predictability of indicator bacteria at specific beaches by associating hydrometeorological predictors and potentially dynamic process models.
Background & Justification
Typically, recreational water is tested for indicators of human fecal contamination in order to safeguard swimmers from exposure to disease-causing organisms. Traditional analytical methods for indicator bacteria require more time than the rate of change of indicator bacteria concentrations, resulting in delayed notification of contamination or alternately unnecessarily closed beaches. Faster and more accurate determinations of surface water quality are of significant importance to better protect public health and maximize recreational use. For example, using ambient hydrometeorological measurements, real-time predictions of the concentration of fecal indicator bacteria can be made, and beach managers can use this information for determining when to close the beach.
This work requires the development of multi-faceted approaches to improve understanding of environmental microbiology and monitoring accuracy and to decrease public health risk. This requires the simultaneous investigation of the abundance, biological characteristics, and potential sources of indicator bacteria populations; approaches to improve the timeliness of monitoring results; and the validity and reliability of the indicator bacteria used in assessments.
Current applications of predictive models include locations throughout the Great Lakes. In my work, I have developed or assisted in developing models at dozens of Lake Michigan beaches, as well as beaches in all other Great Lakes. The application of these models continues to be refined, with newer estimations of predictors, new predictors, and also the understanding that predictive models are not suitable for all locations. Many beach managers are interested in exploring the possibility of using a predictive model, and many are actively pursuing this as a monitoring/management solution.
Several studies have shown that Cladophora mats are a source of enteric human bacterial pathogens (e.g., Salmonella, Campylobacter), potentially influencing shoreline water quality and affecting swimmers health. Equally concerning is the recent hypothesis that Cladophora may have a role in the spread of botulism disease in fish-eating birds of the Great Lakes. A high incidence of botulism in birds parallels with increased Cladophora accumulations in shoreline waters. However, Cladophora role in this disease pathway remains to be elucidated. Moreover, quantifiable (i.e., measurable) health risk to humans or wildlife from direct exposure to Cladophora or Cladophora-laden water/contaminated beach sand deserves further investigation.
- Estimate risk of human exposure to enteric bacterial pathogens in contaminated watersheds and beach ecosystems.
- To investigate Cladophora role in bird botulism:
- To understand the association between Cladophora and Clostridium botulinum, the causal agent of bird botulism.
- To understand food web interactions (involving algal benthic macroinvertebrate communities) in botulism disease pathways.
Background & Justification
Stranded Cladophora mat accumulations are common along shorelines of the Great Lakes during warm summer months, directly affecting visitor enjoyment due to noxious odors from decomposing mats and potentially causing economic losses from reduced recreational days. Numerous studies have shown that Cladophora in nearshore waters can affect beach water quality since the algal mats are known to harbor high levels of the enteric bacteria: E. coli and enterococci, with counts often exceeding 100,000 CFU/g [(4, 7, 9)]. Aside from these commensal bacteria, various human pathogens, such as shiga toxin-producing E. coli, Salmonella, Shigella, and Campylobacter have also been recovered in Cladophora mats [(1, 5)]. It has been postulated that high levels of these bacteria are due to in situ growth [(2, 9)], as the mats are a natural substrate for a variety of micro- and macroorganisms.
There is growing speculation that Cladophora may have a role in bird botulism outbreaks [(3, 6)], a fatal bacterial disease that threatens lake and wetland birds [(8)]. This disease is caused by ingestion of neurotoxins produced by Clostridium botulinum bacteria. The neurotoxin typeE is common in fish-eating lake birds, causing major die-offs in the lower Great Lakes. Some of the commonly affected birds include ring-billed gulls, herring gulls, double-crested cormorants, horned grebes, red-necked grebes, mergansers, common loons, and scoters. In Lake Michigan, botulism outbreaks have been more common in recent years, with beaches around Sleeping Bear Dunes National Lakeshore (SLBE) identified as the epicenter.
C. botulinum bacterium is nearly ubiquitous in the environment â€“ especially, in river, wetland, and lake sediments; however, the mechanism by which the disease manifests in birds remains poorly understood. Fish (e.g., gobies) and macroinvertebrates (e.g., Quagga mussels and other benthic organisms), both identified as part of the food web, have been suggested to play a critical role in disease transmission. High bird mortality at SLBE coincides with massive Cladophora accumulations in benthic habitats at a time when the algae shifts to a heterotrophic condition. Thus, it has been postulated that decaying Cladophora during late summer likely create nutrient-rich, anaerobic conditions that are conducive for the sustenance of C. botulinum [(3)]. One of the pathways might include vegetative cells/spores and/or the toxin itself via the various intermediaries (sediment-Cladophora-invertebrates-fishes) ultimately to birds for piscivorous species. GLSC scientists and their collaborators are studying the role of Cladophora in supporting C. botulinum growth; mussels and other macroinvertebrates in botulism disease transmission; and whether C. botulinum associated with Cladophora mats produces the potent typeE neurotoxin. Generally, current monitoring programs for beach health and botulism outbreaks are relatively less frequently. Therefore, a more frequent/robust monitoring would provide valuable data that could be used to develop better methods to predict and prevent beach closures and botulism outbreaks.