SHOSHONE NATIONAL FOREST—Kelsee Hurshman stepped carefully into the shallows of subalpine Upper Brooks Lake high in the Absaroka Range. 

The lake bottom was muck, and the water looked nasty — pea soup colored, with a bunch of floating thingies. The green, detritus-filled cove was nothing a healthy person would think of drinking from, but a thirsty dog probably wouldn’t hesitate. And this is just what the Wyoming Department of Environmental Quality employee from Cheyenne was looking for. 

The 9,100-foot-high backcountry basin has a history of harmful cyanobacterial — commonly called blue-green algae — blooms. Officials advised the public of a bloom, starting on Aug. 24. Wading in about a month later, Hurshman sought to see if the water contained enough cyanobacteria-associated toxins to warrant an additional advisory. 

“I’m collecting a few different samples,” said Hurshman, DEQ’s harmful cyanobacteria coordinator. Quickly and quietly, she bottled up the algae-choked water.

The remnants of a potentially toxic cyanobacteria bloom linger in a cove of Upper Brooks Lake in September 2023. (Mike Koshmrl/WyoFile)

It was Sept. 20, and Hurshman was sampling with a couple DEQ colleagues and Shoshone National Forest hydrologist Gwen Gerber. The team logged the species of cyanobacteria present, where it was in the water column (the surface) and its color (green). 

Over the course of the day, they’d hike by all the named lakes in the small watershed pressed up against the Continental Divide: first, Brooks Lake, then Upper Brooks, Rainbow and Lower and Upper Jade lakes. 

Rimmed by Sublette Peak, the Breccia Cliffs and the Pinnacle Buttes, the stunning chain of lakes lies entirely in the national forest. They are remote, usually free from human presence and appear pristine. At a glance, one would never associate these picture-postcard-worthy high-altitude lakes with contamination. Yet they are dogged by nutrient problems and cyanobacteria blooms. 

“All of the named lakes have had blooms over advisory levels,” Gerber said, “and two of them have had toxins over advisory levels.” 

Many unknowns

A mysterious environmental influence — or combination of factors — is believed to be triggering the blooms. There are theories, but DEQ employee Ron Steg, who leads the agency’s Lander office, is clear: There’s no saying exactly why cyanobacteria are striking this area every summer. 

“This particular watershed, the geology is high in phosphate,” Steg said. “It could be atmospheric deposition. We don’t know, and that’s why we are studying this.” 

Shoshone National Forest hydrologist Gwen Gerber and Wyoming Department of Environmental Quality staffers Kelsee Hurshman, Ron Steg and Jillian Scott check out the shoreline of Brooks Lake Creek just below the outflow from Upper Brooks Lake. Although the water flows through a remote, wild, high-altitude landscape, the watershed is plagued by potentially harmful algal blooms. (Mike Koshmrl/WyoFile)

The DEQ is specifically examining what’s going on in the Brooks Lake watershed in detail because its 234-acre namesake lake has struggled with algal blooms that, on the worst occasions, have been implicated in fish kills so severe that fish went belly up miles downstream in the Wind River. Since 2018, Brooks Lake has occupied a slot on the Wyoming DEQ’s “impaired list.” At one time, fingers were pointed at Brooks Lake Lodge and its formerly surface-discharging sewage lagoon, but problems with nutrients and cyanobacterial blooms higher in the watershed have led to a more holistic investigation. 

The Brooks Lake watershed, however, isn’t the only place in Wyoming where people and their pets are finding harmful cyanobacteria blooms in unlikely places. 

Late last October, the Wyoming Department of Health issued a recreation advisory for the Wind River after a 10-pound puppy died within minutes of drinking flowing river water near the Upper Wind River Campground. Campers be forewarned: there are fall 2023 cyanobacteria toxin advisories in place for both the upper and lower Wind River campgrounds, plus in the Wind River immediately below Boysen Reservoir and two areas in the reservoir itself.

“It sounded like the animal wasn’t taken to the vet because the dog died so quickly,” Lindsay Patterson, DEQ’s surface water quality standards coordinator, said of the 2022 puppy death.

A species of cyanobacteria that resembles grass clippings floats in the water near the Brooks Lake boat ramp in September 2023. (Mike Koshmrl/WyoFile)

Those types of fast-acting cyanobacteria dog deaths can happen when canines ingest chunks of “mat-forming blooms.” Water quality specialists don’t know if one of the harmful mats came off Boysen Reservoir, flowed past the dam and stayed intact enough to still be deadly when the puppy encountered it a mile downstream, or if the mat formed in the Wind River itself. 

Late summer and early fall are typically when cyanobacterial blooms are most likely to occur, but that’s not always the case. 

In December of 2021, ice fisherman augering through a frozen-over Keyhole Reservoir came into a blue-green algae bloom. Three months later DEQ officials were still able to sample cyanobacteria in densities that exceeded the recreational standard. 

“We went back and looked at the satellite imagery from before and it looked really, really bad,” Hurshman said. “We suspect it may have persisted.” 

Then there’s the backcountry. Cyanobacteria blooms are often associated with abundances of nutrients, like fertilizer from agriculture, and warm water typically found at lower elevations. So why are blooms showing up in places like Togwotee Pass?

Shoshone National Forest hydrologist Gwen Gerber leads Wyoming Department of Environmental Quality staffers Kelsee Hurshman, Ron Steg and Jillian Scott past Brooks Lake on the hike to Upper Brooks Lake, part of a years-long investigation into nutrient imbalances and seasonal algal blooms that plague the high-elevation watershed. (Mike Koshmrl/WyoFile)

Gerber, the Shoshone National Forest hydrologist, doesn’t have any firm answers, but she has noticed a trend within the 17 waterbodies on the national forest where cyanobacteria have been detected in high enough concentrations to warrant an advisory. All of them except for one, she said, are located in the Absaroka Volcanic formation — which suggests a component of the geology could be a contributing factor. 

Finding new hazards

That’s not to say that potentially harmful blue-green algae blooms are restricted to those 17 lakes on the Shoshone National Forest. The hazard could be much more widespread, but documenting each instance with limited staff and time isn’t practical.

“We can’t go to all the lakes every year,” Gerber said. 

This year Gerber went in to test three new lakes in the East Dunoir Creek watershed on the hunch that there might be blooms because lakes in an adjoining watershed — West Dunoir Creek — have had issues. 

“Two of those water bodies had blooms above advisory levels,” Gerber said. 

The DEQ’s website currently lists advisories for North and South Watkins lakes. 

Judging by the DEQ’s interactive advisory map alone, which is cataloged by year, known harmful cyanobacterial blooms are rapidly increasing in Wyoming waters. As recently as 2017 there were only three advisories in the entire state. By 2020 the list grew to 21 lakes statewide. Even after a long-lasting winter and cool spring — conditions that theoretically keep blooms at bay — there have already been 47 advisories posted so far in 2023.

Cyanobacteria blooms in densities above advisory levels have been documented in all corners of Wyoming during 2023. (Wyoming Department of Environmental Quality)

There’s evidence, however, that the increase is not strictly a symptom of environmental change. Increased reporting by a better-educated populace that now knows what to look for appears to be contributing to the rise in numbers. 

What might have just looked like a scummy pond in the yesteryear is now reported, sampled, tested and classified as a waterbody with a cyanobacterial bloom advisory. Anne’s Pond, for example, a tiny algae-choked feature on a hiking trail south of Jackson, now shows up with an advisory on the DEQ’s website. And an unnamed “Palmer Creek Trail Pond,” just a few miles away, is under investigation. 

Research backs up the claim that the increase in known cyanobacteria blooms is a product of looking harder and testing for it. The DEQ recently funded University of Wyoming research that evaluated 40 years of satellite imagery, including 200 lakes in Wyoming. 

“That study seems to indicate that we’re probably getting better at identifying blooms and there’s more awareness,” Patterson said, “rather than that we’re seeing a really large increase in the blooms.” 

Cyanotoxins, she said, were pretty much unknown to most people until Toledo, Ohio’s drinking water was affected in 2014. 

“At water quality management agencies, some people were doing some monitoring here and there,” Patterson said. “But it was not like the robust programs that you see now.” 

Scaling up

That holds true for the Wyoming DEQ. Hurshman’s position didn’t exist until around 2018, and it’s become progressively more focused on harmful cyanobacteria monitoring, Patterson said. In 2021 the agency began a routine monitoring program that prioritizes water where people tend to recreate, and where blooms are most likely to produce toxins. This year they brought on an intern also devoted to the monitoring cause. Hurshman also conducts routine satellite monitoring of 40 of the state’s lakes and reservoirs, which allows her to track the seasonal evolution of blooms — and feed data into the interagency Cyanobacteria Assessment Network.

The gloved hand of Wyoming Department of Environmental Quality staffer Kelsee Hurshman, the agency’s harmful cyanobacteria program coordinator, grasps a bottle full of algae-choked water extracted from Upper Brooks Lake on the Shoshone National Forest. (Mike Koshmrl/WyoFile)

“It’s been a major priority for us,” Patterson said of cyanobacteria monitoring. “In Wyoming, I think we now have a better idea of where [blooms] are, and which ones are producing toxins. But we do have to make choices in how we’re allocating resources.” 

Many smaller backcountry Wyoming lakes prone to harmful cyanobacteria blooms will likely never be sampled every summer — or perhaps even ever.

But others, like those in the chain of lakes where Hurshman hiked north of Togwotee Pass, are likely to be monitored annually and even be subject to special studies. There, the intensive effort is a result of Brooks Lake’s impaired classification in the Wyoming DEQ’s 305B and 303D report, which is required by the Environmental Protection Agency under the Clean Water Act. 

Brooks Lakes’ impairment is listed as “not fully supporting” its fishery and other aquatic life due to an abundance of nutrients and elevated pH. DEQ officials, in turn, are trying to understand what, if anything, they can do to improve the water quality. 

To that end, DEQ employees Tavis Eddy and Val Shao pumped up packrafts to float out and measure for temperature, pH and other parameters a half mile up the trail from Upper Brooks Lake at Rainbow Lake back on Sept. 20. The boat-borne data collection was part of a three-year-long intensive monitoring effort that’s not yet completed. Eventually, the data they gather could help explain the factors plaguing the Brooks Lake system. 

Val Shao, a water technician for the Wyoming Department of Environmental Quality, paddles a packraft toward the center of Rainbow Lake to conduct tests with Tavis Eddy, an environmental scientist with DEQ’s water quality program. The DEQ has monitored Rainbow Lake and other portions of the Brooks Lake watershed for several years to help determine what’s been causing nutrient-driven algal blooms. (Mike Koshmrl/WyoFile)

But in the meantime, scientists like Steg hesitate to hazard a guess as to what exactly is going on. 

“The whole purpose of what we’re doing here is to determine the causes and sources [of nutrients],” he said. “Another year and hopefully we’ll have some real data and can come up with some real answers.” 

Some answers will come sooner, like whether Upper Brooks Lake and other reaches of the watershed are dangerous to people’s pets this fall. The cyanotoxin lab results are already in. Hurshman’s samples from Upper Brooks Lake did not exceed the toxin threshold, but the water she gathered at Rainbow Lake did. See the details about that cyanobacteria hazard — and 17 other known toxic waters in Wyoming —  at the DEQ’s advisory website.

Mike Koshmrl reports on Wyoming's wildlife and natural resources. Prior to joining WyoFile, he spent nearly a decade covering the Greater Yellowstone Ecosystem’s wild places and creatures for the Jackson...

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  1. Just curious. Would all the backcountry water treatment methods effectively neutralize these toxins and bacteria? Steri-Pen, filtration, boiling, chemicals??

      1. Thanks! I do a lot of backpacking in the southern Utah canyons. Sometimes my only water source is pretty nasty is pretty nasty looking.

  2. I thought I read somewhere that some scientists felt that the increase in fires in the west was dropping enough particles into lakes to encourage growth of Cyanobacteria. Kind of makes sense for pristine high altitude lakes having the same problems as lower lakes

  3. Not a real big mystery where it comes from. Fire retardants dropped contain NPK. THAT washes into water shed. Also leaves/organic matter decompose in water.