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An algae bloom with the potential to produce harmful toxins has been identified at Hyalite Reservoir, one of Bozeman’s most popular outdoor recreation sites.

The Gallatin City-County Health Department is advising visitors to the reservoir south of Bozeman to be cautious and avoid any algae bloom suspended in water that looks “like pea soup, grass clippings or green latex paint,” according to a Friday news release.

The algae bloom can produce toxins that are harmful to people, pets and livestock. Direct contact, ingestion or inhalation of the toxins may irritate the skin, eyes, nose and respiratory system or cause nausea, vomiting, diarrhea or headaches, according to the new release.

Lori Christenson, environmental health director for the health department, urged visitors to the reservoir to not take any chances.

“When in doubt, stay out. Do not drink, swallow, or swim in water that shows signs of a (harmful algae bloom) and be sure to keep kids, pets and livestock out too,” Christenson said in the news release.

The health department advises anyone who suspects a HAB-related illness in a person or animal to call poison control at 1-800-222-1222 or to seek medical attention.

Hannah Reidl, a water quality specialist at the Montana Department of Environmental Quality, which tracks harmful algae blooms (HAB) throughout the state, said in the news release that children and pets are especially at risk.

“Children and pets are more likely to ingest HAB-infested waters because they spend most of their time wading in the shallow waters where algae can accumulate, and they have less control over how much water they ingest,” Reidl said.

The city of Bozeman is confident its water supply is not affected, according to the news release. Staff collect and test water samples from multiple sources in Hyalite every week.

DEQ asks recreationists for help in tracking algae blooms by submitting photos to or by calling 1-888-849-2938. The website includes a live map that shows where other harmful algae blooms have been identified.

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Shaylee Ragar can be reached at or at 582-2607.

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