A cyanobacteria bloom is visible in the bluish-green waters at Flaming Gorge Reservoir in 2019. (Courtesy Wyoming Department of Environmental Quality)

Wyoming health officials are again warning of dangerous summer blooms in lakes, ponds and reservoirs, blooms that can kill dogs and make people ill. 

As of publication, only three lakes or reservoirs have toxin advisories listed: Goshen Hole Reservoir, Leazenby Lake and Eden Reservoir. Many additional bodies of water have bloom advisories.  

Harmful cyanobacterial blooms vary in appearance, usually ranging from bluish-green to green or brown in color. Blooms can look like floating mats, grass clippings, cottage cheese, discolored water, scum or spilled paint and can last up to months, according to the Department of Environmental Quality.

Suspected cyanobacteria blooms can be reported to the DEQ. Related illnesses can be reported to the Wyoming Department of Health.

The DEQ saw harmful cyanobacterial blooms as late as November last year, Kelsee Hurshman, HCB coordinator at the agency, said.

At low concentrations, in which they occur naturally, cyanobacteria can be harmless, and sometimes they don’t produce toxins at all. In warm, stagnant and nutrient-rich water, however, they can accumulate to dangerous levels.

Brown mats in Leazenby Lake — or Hundred Springs Reservoir — indicate a dangerous bloom. WDH has issued both bloom and toxin advisories for the lake this summer. (Courtesy Wyoming Department of Environmental Quality)

“Multiple toxin types may be produced by a single species and cyanotoxins can persist in the ecosystem after a bloom subsides with length of time varying between toxin type and environmental conditions,” University of Wyoming Ph.D. student Ashleigh Pilkerton told WyoFile via email. “As a scientific community, we still have much to learn about cyanotoxins and why they are produced.” 

Cyanobacteria aren’t all bad. Scientists even believe they provided the oxygen leading up to the “Great Oxidation Event” of Earth’s atmosphere over two billion years ago, paving the way for the evolution of multicellular organisms.  

Research provides insight  

Because awareness, reporting and monitoring of blooms have improved, it can be difficult to tell if blooms are getting worse or just drawing more attention. Sam Sillen, a graduate student at UW, looked at satellite imagery dating back to 1984 to address that question.  

Sillen used the images to predict concentrations of chlorophyll a in lakes around the state. Chlorophyll is a green pigment used in photosynthesis, and chlorophyll a is just one form of the substance. Also present in algae and plants, it isn’t a perfect indicator for cyanobacteria but can still act as a helpful proxy. 

“Looking at the chlorophyll a predictions over this 40-year timespan, what we find is a lot of lakes have a history of either being relatively eutrophic or having a high chlorophyll a concentration, and few lakes are rapidly increasing in terms of their chlorophyll a, likely leaning towards this historical baseline of a lot of algal blooms in Wyoming,” Sillen said. “On the other hand, there is a subsection of lakes that are becoming more eutrophic or increasing in chlorophyll a.” 

Eutrophic refers to bodies of water with excessive nutrients and an overabundance of photosynthetic organisms. Sillen is working to understand what factors are driving changes in that subsection of lakes.

A cyanobacteria bloom is visible in the waters of Toltec Reservoir in July 2022. (Courtesy Wyoming Department of Environmental Quality)

Another portion of Sillen’s research is to evaluate the remote sensing tool used by the DEQ to monitor blooms. He is comparing results from samples to the remote sensing estimates gathered from satellite images. 

Pilkerton’s research focuses on the ecological consequences of harmful cyanobacterial blooms including impacts on other microbial communities, effects on zooplankton species and changes in fish diets. 

On the lookout 

People should avoid cyanobacteria blooms and keep their animals away too, Hurshman said. Anglers should only eat fillets from their fish. If humans or animals are exposed to a cyanobacteria bloom, WDH advises to rinse with clean water and seek medical attention if symptoms arise.  

While contact with skin can be harmful, ingestion poses the greatest health risks, Lindsay Patterson, the DEQ’s water quality standards supervisor, said. Treatments like filtration and boiling do not remove toxins, according to WDH.  

Dogs and other animals can die as a result of ingesting bloom materials, and while more uncommon, humans can also get seriously ill from exposure. 

Sometimes called “blue-green algae,” the toxin-producing organisms that proliferate across Wyoming’s waters around this time of year are instead a type of photosynthetic bacteria, distinct from algae in both their evolution and cellular biology. 

Cyanobacteria blooms can be distinguished from algae and aquatic plants because “individual cyanobacteria are small and do not form long, filamentous networks.” Because of that, scums or mats of the dangerous cyanobacteria can be easily broken apart, according to the DEQ. Their FAQ site suggests simple tests using a stick or jar to help distinguish a cyanobacteria bloom.  

Testing the waters 

In addition to looking for visual evidence of cyanobacteria, Wyoming recreationists can check an advisories map of the state to see where toxin and bloom advisories are listed and those that are still under investigation. WDH issues advisories based on data provided by the DEQ. 

The map provides information about the types and concentrations of cyanobacteria and cyanotoxins that have been tested for, as well as sampling dates and locations. 

A water body may have a bloom advisory but no toxin advisory because samples are still being analyzed or because sampling demonstrated elevated cyanobacteria levels but not elevated toxin levels. However, this doesn’t necessarily mean that the waters are safe. 

“The conditions of cyanotoxin concentrations on the water body can change very quickly,” Hurshman said. 

A cyanobacteria bloom proliferates on the shores of Big Sandy Reservoir in 2020. (Courtesy Wyoming Department of Environmental Quality)

Routine monitoring for harmful cyanobacterial blooms in the state occurs through both on-the-ground sampling and via satellite imagery processed by the Environmental Protection Agency’s Cyanobacteria Assessment Network and evaluated by Hurshman. 

“There’s a number of water bodies that blooms occur on every single summer, pretty much like clockwork, so to speak,” the DEQ’s Patterson said. “Then there’s a handful that we’ll be made aware of.”

Before 2021, the DEQ only investigated for cyanobacteria and cyanotoxins in response to reports of blooms or as prompted by the CyAN satellite imagery. Last year the agency implemented an additional monthly monitoring system for 25 high-priority bodies of water with heavy recreation use and where harmful blooms are common. 

Every month, the DEQ conducts visits to high-recreation locations at each water body on the list, investigates for signs of cyanobacteria blooms and collects samples for analysis where blooms appear.

While the routine monitoring program has already helped the DEQ figure out where elevated levels of cyanotoxins occur frequently, Patterson and Hurshman are hoping that it will also help them better understand the conditions that lead to toxin production and whether blooms are becoming more or less toxic. 

Hurshman reviewed last year’s data but didn’t discover any trends. Information from this year will be added to the dataset for further analysis. 

Addressing nutrient pollution 

Nutrient availability is an important factor, and “nitrogen and phosphorus are the two most important nutrients” for driving harmful blooms, Pilkerton said.  

The DEQ is collaborating with the Wyoming Nutrient Work Group, a diverse stakeholder group, to tackle nutrient pollution in Wyoming waters. The group will work to “identify water bodies where there are excess nutrients and then develop restoration plans for those water bodies,” Patterson said.  

One of those is Boysen Reservoir, where the group is already coordinating with stakeholders to reduce nutrient inputs and resulting blooms.  

Nutrient sources can include stormwater and agricultural runoff, lawn fertilizers, septic tanks, wastewater treatment plants, industrial discharges, atmospheric deposition, and lake turnover, Patterson said.

This story is supported by a grant through Wyoming’s Established Program to Stimulate Competitive Research (EPSCoR) and the National Science Foundation.

Andromeda Erikson is a 2022 science journalism intern at WyoFile. She lives in Laramie and studies environmental sciences and journalism at the University of Wyoming. Contact her at aerikson@uwyo.edu.

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  1. I believe Boysen is the body of water that the gas well water discharge will flow to. Oil feild waters are naturally rich in mineral nutrients. Gas wells are especially high in Ammounia as N. NITROGEN FOLKS. So it not hard to figure out the state of Wyoming is allowing a huge nutrient load into the lake. Nitrogen is key to microbes cell wall strength when they divide. This issue will get worse and worse.

  2. It’s not hard to figure out. There are economical solutions. But no one wants to implement them. It’s always “get a grant and “study” the issues”. Year after year same thing.