Harmful algae advisory issued for portion of Guernsey Reservoir
TORRINGTON (WNE) – State health and environmental officials have issued a Harmful Cyanobacteria Bloom Recreational Use Advisory for a portion of Guernsey Reservoir after water sampling detected potentially harmful levels of cyanobacteria.
The advisory, issued June 19 by the Wyoming Department of Environmental Quality and the Wyoming Department of Health, applies to the Black Canyon Cove Campground area of the reservoir.
Officials stress that Guernsey Reservoir remains open to the public, but visitors are urged to use caution and avoid contact with water in the affected area.
Cyanobacteria, commonly referred to as blue-green algae, can produce toxins that pose health risks to people, pets and livestock. Exposure to cyanotoxins can occur through swimming, wading, accidental ingestion of contaminated water or contact with algae.
Symptoms in people may include skin irritation, gastrointestinal illness and other health effects, while pets, particularly dogs, can become seriously ill after swimming in or drinking contaminated water.
The DEQ and WDH recommend that recreationists avoid swimming or wading in areas where algae is visible, especially where thick mats or surface scum are present.
Officials also advise against drinking untreated water from the reservoir, noting that boiling or filtering the water does not remove cyanotoxins.
Pet owners and livestock producers are encouraged to keep animals away from the affected water, as animals are especially vulnerable after ingesting contaminated water or algae.
State officials said anglers may continue fishing at the reservoir. Fish are considered safe to eat when properly cleaned, provided anglers rinse them with clean water and consume only the fillets, discarding the guts.
Cyanobacteria blooms occur naturally but can become harmful when environmental conditions such as warm temperatures, sunlight and nutrient-rich water allow the organisms to multiply rapidly. Blooms may appear as green, paint-like scum, floating mats, or discolored water, and can change in location or intensity as weather conditions shift.
This story was published on June 24, 2026.
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