LARAMIE -- The Wyoming Department of Health has issued a recreational use advisory for Toltec Reservoir in Albany County due to a harmful cyanobacterial bloom. HCBs are also referred to as harmful algal blooms since cyanobacteria are commonly known as blue-green algae.

The Department of Health issues advisories to inform the public that there may be health risks for people and animals in areas where HCBs occur. Lakes and reservoirs under a recreational use advisory are not closed since HCBs may only be present in certain areas of the waterbody and conditions can change frequently. The advisory will remain in place until the bloom has fully dissipated.

This advisory follows an HCB advisory at Leazenby Lake near Laramie 2 weeks ago. Dr. Karl Musgrave of the WY dept. of public health, told LaramieLive that the Leazenby Lake advisory is still in effect, and these advisories usually stay in effect until October or November when the weather turns colder and causes the bloom to dissipate. 

On July 26, the Wyoming Game and Fish Department received a complaint from a landowner that Toltec Reservoir was experiencing a bloom. The Wyoming Department of Environmental Quality visited the reservoir on July 29 and collected water samples at a boat launch of the public access area. Cyanobacteria densities exceeded the 20,000 cells/mL recreational use threshold identified in Wyoming’s Harmful Cyanobacterial Bloom Action Plan. Cyanotoxin results are pending. The most up-to-date information, as well as other HCB resources, can be found at

According to, many types of algae can cause HABs in freshwater systems. The most frequent and severe blooms involve the proliferation of cyanobacteria. Some cyanobacteria species can produce toxins—cyanotoxins—that can cause mild to severe health effects in humans and kill aquatic life and other animals.

HABs can also contribute to deteriorating water quality and ecosystem health. As masses of cyanobacteria or other algae die and decompose, they consume oxygen, sometimes forming “dead zones” where life cannot survive. These areas can kill fish and organisms, such as crabs and clams, and have detrimental economic effects.

Scientists widely consider nutrient enrichment to be a key cause of HAB formation. While nutrients are essential to plants and natural parts of aquatic ecosystems, excessive amounts can overstimulate algal growth. Sources include point sources (e.g., municipal wastewater discharges) and nonpoint sources (e.g., fertilizer runoff from agricultural and urban areas).

The Wyoming Department of Health is working directly with the Wyoming Game and Fish Department to post advisory signs at the reservoir.

The Wyoming Department of Health and Wyoming Livestock Board recommend the following:

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

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 and contact a doctor or veterinarian.

Questions about health effects and recreational use advisories can be directed to Dr. Karl Musgrave, State Environmental Health Epidemiologist / State Public Health Veterinarian, Wyoming Department of Health, at or (307) 777-5825.

Questions regarding cyanobacteria sampling can be directed to Michael Thomas, Natural Resource Analyst, Wyoming Department of Environmental Quality, at or (307) 777-2073, or Lindsay Patterson, Surface Water Quality Standards Coordinator, Wyoming Department of Environmental Quality, at or (307) 777-7079.


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