Subscribe to our Daily Headlines newsletter.

A harmful algal bloom at the Lake Helena Wildlife Management Area boat launch.

Caution advisories have been issued for harmful algal blooms at the Lake Helena Wildlife Management Area boat launch and the nearby Hauser Reservoir Causeway.

The advisory for Lake Helena was issued Thursday, after teal blue/turquoise foamy patches mixed with other floating algae and vegetation was observed. Some larger patches had a light blue, stringy appearance extending below the water surface, according to a description provided to the Montana Department of Environmental Quality.

The advisory for the Hauser Reservoir Causeway was issued July 23, after a kayaker reported splotches of turquoise on the surface of the water along the shoreline. 

Two caution advisories were previously issued on Canyon Ferry Lake. One was issued July 14 near the Hellgate Campground and one was issued July 9 in the Duck Creek area. 

Public health officials urge people to know the health risks of the blooms, also known as HABs, which are caused by blue-green algae that are native to Montana’s freshwater lakes and reservoirs. They could produce toxins that can harm people, pets and livestock.

Not all varieties are harmful, but some can produce dangerous cyanotoxin. Blue-green algae blooms often look like pea soup, grass clippings or green latex paint, officials said. They are usually suspended in the water or appear as floating mats; they do not grow from the bottom with roots like other water plants.

Children and pets are more likely to ingest HAB 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.

Ongoing high temperatures could increase algal bloom activity.

Officials said those who catch fish in waters where blooms have been reported should discard all of the fish's organs and clean it well. They also cautioned people not to touch the water.

People can help by reporting HABs so that officials can respond quickly. Suspected HABs can be submitted, including photos, to the website: www.hab.mt.gov. This site also has a live map of reported HABs and identification information.

Direct contact, ingestion or inhalation of cyanotoxins may irritate the skin, eyes, nose and respiratory system or cause nausea, vomiting, diarrhea or headaches. If you suspect a HAB-related illness in a person or animal, call Poison Control 1-800-222-1222 and seek medical attention.

Those who suspect a HAB should file a report at www.hab.mt.gov or call 1-888-849-2938, or call Lewis & Clark Public Health, Environmental Health Division, at 406-447-8351.

Subscribe to our Daily Headlines newsletter.

A harmful algal bloom has been found at Canyon Ferry Reservoir near the Hellgate Campground Day Use Area and Boat Launch. 

The Montana Department of Environmental Quality on Tuesday issued a caution advisory for a harmful algal bloom in Duck Creek on Canyon Ferry Reservoir.

A harmful algal bloom at the Lake Helena Wildlife Management Area boat launch.

Get up-to-the-minute news sent straight to your device.