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Spokane, Washington  Est. May 19, 1883
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11 bodies of water in North Idaho have been hit by toxic algae this year compared to three last year – here’s what’s going on

Oct. 8, 2021 Updated Wed., Oct. 13, 2021 at 7:18 p.m.

Algae floats in Fernan Lake on Aug. 2.  (Kathy Plonka/The Spokesman-Review)
Algae floats in Fernan Lake on Aug. 2. (Kathy Plonka/The Spokesman-Review)

Scorching temperatures led to a steep increase in public health advisories for harmful algae blooms this year in northern Idaho bodies of water.

Eleven advisories related to harmful algae blooms, or blue-green algae, have been issued so far this year compared to three last year, said Panhandle Health District spokesperson Katherine Hoyer.

The health district and the Idaho Department of Environmental Quality issued advisories Thursday for Cave Lake and Hauser Lake in Kootenai County.

Hoyer said the consistent hot temperatures over the summer played a major factor in the development of blue-green algae.

“That really plays a large role in any type of organism growth in water,” she said. “As the water bodies heat up, it’s a breeding ground for different types of organisms, and unfortunately, harmful algal blooms are one of those.”

Increased nutrients in the water and stagnant water are contributing factors to the growth of the algae.

The district this year also issued health advisories due to harmful blooms at Fernan Lake, Hayden Lake, Spirit Lake and Sagle Slough, where the Pend Oreille River meets Lake Pend Oreille, to name a handful.

Some lakes, like Fernan, Spirit and Cocolalla, receive regular advisories, Hoyer said. She said one is issued for Fernan almost every year.

One year, Fernan Lake bloomed and it did not reach a level low enough to lift the advisory until the winter, Hoyer said.

She said the advisories typically start being issued in July and August.

Hoyer said it is difficult to predict if the frequent advisories will continue next year, but if the hot summers continue, it is possible.

DEQ tests the shoreline, where the algae is often found, as well as deeper water.

The health district and DEQ urge the public to use caution when recreating in or near water with harmful blooms, according to the district’s news release regarding Cave and Hauser lakes.

Caution should be taken anywhere the water appears discolored or murky as blooms can spread or move with wind and water currents. Blooms have the potential to produce dangerous toxins, especially when accumulated in high concentrations.

The physical appearance of the blooms can be unsightly, often presenting as discolored water, streaks or globs of scum and causing thick green mats along lake shorelines. Pets, children, the elderly and people with compromised immune systems are most at risk of harmful exposure, and several pets are believed to have died after coming into contact with the toxins this year in the Spokane area.

If contact is made with water containing harmful blooms, it is recommended to wash off with fresh water.

Symptoms of exposure to algal toxins vary according to exposure. They can include rashes, hives, diarrhea, vomiting, coughing or wheezing. More severe symptoms affecting the liver and nervous system may result from ingestion of water. If symptoms persist, consult a health care provider.

The public will be advised when the concern no longer exists at Cave and Hauser lakes.

Updated information on harmful algae blooms in northern Idaho can be found online at

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