Toxic algae bloom advisory in effect at Pathfinder Reservoir - Casper, WY Oil City News
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Toxic algae bloom advisory in effect at Pathfinder Reservoir

A blue-green algae bloom at Pathfinder Reservoir in 2018. (Wyoming DEQ)

CASPER, Wyo. — A harmful cyanobaterical bloom advisory has been issued for Pathfinder Reservoir.

Satellite imagery confirmed elevated level of the blooms, which are also known as blue-green algae blooms, covering large portions of Pathfinder on Aug. 26, the Wyoming Department of Environmental Quality says.

Water samples showed that cyanobacterial cell densities exceed 20,000 cells per millimeter in the water.

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“Cyanobacteria…can form blooms that produce toxins and other irritants that pose a risk to human, pet and livestock health,” the department says.

Thursday’s announcement follows an advisory for Boysen Reservoir announced on Wednesday.

Current bodies of water with DEQ advisories of the harmful blooms are available online. 

People can report waters where they suspect harmful blooms are present online or by calling (307) 777-7501

“Advisories are issued by the Wyoming Department of Health when cyanobacterial cell densities and/or cyanotoxin concentrations may pose a health risk to people in areas where cyanobacterial blooms occur,” DEQ explains.

“Blooms may only be present in certain areas of the waterbody and conditions may change frequently.”

DEQ, the Wyoming Department of Health and the Wyoming Livestock Board have been receiving increasing inquiries about the harmful blooms.

Such blooms generally form in standing or slow-moving water and as temperatures increase throughout the summer.

“They are episodic and can last for a few hours or a number of months,” DEQ says.

A previous advisory for Pathfinder Reservoir was issued in Sept. 2018, but was lifted in November. Alcova had an advisory for the same time frame.

The following tips are recommended when harmful blooms are present:

-Avoid contact with water in the vicinity of the bloom, especially in areas where cyanobacteria are dense and form scum.

-Do not ingest water from the bloom. Boiling, filtration and/or other treatments will not remove toxins.

-Rinse fish with clean water and eat only the fillet portion.

-Avoid water spray from the bloom.

-Do not allow pets or livestock to drink water near the bloom, eat bloom material or lick fur after contact.

-If people, pets or livestock come into contact with a bloom, rinse off with clean water as soon as possible.

Wyoming Department of Environmental Quality

If people or animals come in contact with blooms and experience “adverse health effects after exposure,” they should seek immediate medical or veterinary attention.

“Young children, pregnant women, people with weak immune systems and animals are especially at risk,” DEQ says. “Questions regarding general health risks and symptoms related to a cyanobacterial bloom can be referred to Dr. Karl Musgrave, State Public Health Veterinarian and Environmental Health Epidemiologist with WDH at 307-777-5825.”

“More health information is also available at”

“For additional information on HCBs in Wyoming and to sign up for advisory updates, please visit”