Researchers are looking for clues as poisonous flowers plague Wyo waters

It can look like green paint spilled onto the surface of a lake. Or like cottage cheese. Or cut grass.

Many people call it blue-green algae, although cyanobacteria are quite a long way from algae on the Tree of Life.

With summer approaching its late stages, chances are good Wyoming residents have noticed. Dangerous blooms tend to infest waterways in mid to late summer and can release toxins powerful enough to kill dogs and even cows.

“Cyanobacteria are naturally found in small quantities in aquatic ecosystems, but they can reproduce under ideal conditions – that is often when temperatures are elevated, when there is still or slow-flowing water, or when nutrient levels are elevated,” said Lindsay Patterson , Surface Water Quality Standards Supervisor for the Wyoming Department of Environmental Quality. “The wind can also aggregate them in parts of water.”

Health warnings about cyanobacteria blooms also spread across the state this summer, from Brooks Lake and Pelham Lake in Shoshone National Forest to Boysen Reservoir in central Wyoming to Sloans Lake in Cheyenne, leading many recreational athletes and even researchers to ask: will these Flowers worse? ?

The long answer is complicated. The short one is: maybe.

“The more people become familiar with the topic and the health risks, the more we hear and actively seek out them,” Patterson said. “I wouldn’t say they’ll necessarily gain weight, but it’s hard to pull it apart.”

Increasing awareness

Cyanobacteria evolved about 3 billion years ago. Not all emit toxins, and most cyanobacteria are not harmful in small amounts. When concentration increases, problems begin.

A bloom of cyanobacteria at Wheatland Reservoir # 3 on August 24, 2021 (Wyoming Department of Environmental Quality)

Poisonous flowers form for a variety of reasons, including warm weather and stagnant water. Although they are most commonly associated with deeper reservoirs and locations where nutrient runoff from agriculture, fertilizers, urban areas, sewage treatment plants, oil and gas plants, or sewage treatment plants is high, they are not exclusively formed in areas with direct runoff. For reasons that researchers are still trying to analyze, the US Forest Service is discovering more of them in high mountain lakes, which could be due to air pollution or nutrient cycling from forest fires or even beetle-killing trees.

It wasn’t until about 2014 when the state (and nation) started taking cyanobacteria blooms more seriously. The city of Toledo, Ohio, found in Lake Erie high enough toxin levels from a cyanobacterial bloom that officials turned off water for about 400,000 people.

“Since then, there has been a much more concerted effort to study these and see how widespread they are,” Patterson said.

In Wyoming, that effort includes satellite monitoring of 40 of the state’s lakes and reservoirs. The satellite scans each body of water and the images are taken from the Cyanobacteria Assessment Network, a conglomerate of federal agencies. Kelsee Hurshman, natural resource analyst at Wyoming DEQ, then uses these processed images to track the flower’s development over the summer.

The effort produces more and more flowers. Once it is confirmed that there is an increased density of cyanobacteria, the Wyoming Department of Health warns the public.

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In large quantities, cyanobacterial toxins can be strong enough to kill a cow if it drinks the water with the flower. They can also kill dogs and cause irritation to human skin. Health advice urges people not to swim in areas with flowers and carefully fillet and discard any fish caught in areas with flowers.

Corresponding The Environmental Protection Agency“Although there are relatively few documented cases of severe human health effects, exposure to cyanobacteria or their toxins can cause allergic reactions such as rashes, eye irritation, respiratory symptoms, and in some cases gastroenteritis, liver and kidney failure, or death.”

A future full of flowers?

Once a flower forms, it usually doesn’t go away until late fall in Wyoming, when sea temperatures drop enough to kill many of the cells, which then sink to the bottom and are consumed by microbes.

While Patterson isn’t sure whether or not the blooms are increasing, the warming temperatures caused by climate change certainly aren’t helping, she said. And she added that late summer blooms and health department warnings are likely to increase in the future as long as surveillance continues.

That’s partly why research is so important, Patterson said.

An aphanizomenon cyanobacterial bloom at Woodruff Narrows Reservoir on July 27, 2021. (Wyoming Department of Environmental Quality)

Sarah Collins, assistant professor of zoology and physiology at the University of Wyoming, is leading a project that compares these satellite images with what exists locally. The team is also developing genomic techniques to identify which types of cyanobacteria are responsible for flowers and how many toxins they produce.

Once some of this information is better understood, researchers and water managers can begin talking about solutions.

Smaller, private ponds have a few simpler potential solutions, Patterson said. Landowners can line the shores of the lake or pond with barley straw, she said, which appears to be deterring flowering.

Aerators can also help by forcing the water to move and not allow flower formation.

However, neither is exactly practical with a reservoir the size of Boysen or Flaming Gorge.

Limiting pollutant inputs from nutrients could also help, though Patterson warned that reducing pollution wouldn’t solve all of the flowers.

“I don’t want to mislead anyone and say that if we take care of the nutrients, the problem will be 100% resolved,” said Patterson. “It will certainly help, and is one thing we can work on by regulating some point discharges and working with non-point discharges to keep nutrients on the ground or out of waterways.”

Patterson also reminds people that just because a body of water has a clue, it isn’t dangerous. The flower could be in an arm of a lake where the water stagnates and stays warm. Other parts of the lake might be fine.

“We don’t want to stop everyone from reinventing themselves,” Patterson said. “Certain activities are less risky than others. If you are fishing or in a boat and not having much contact with a flower, the risks are reduced. ”

A cyanobacteria bloom on August 24, 2021 at Rainbow Lake. The dominant cyanobacteria in this flower are Aphanizomenon and Dolichospermum. (Shoshone National Forest / Wyoming Department of Environmental Quality)

For more information on toxic cyanobacteria or to report a possible bloom, visit For more information on the human health implications, see

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