Oregon Officials Keep Eyes on Lakes for Harmful Algae, Including Near the Coast

Published 06/30/25 at 5:55 a.m.
By Oregon Coast Beach Connection Staff

(Reedsport, Oregon) – It's an odd irony that in the ocean many forms of algae (like diatoms) are a good thing, but for inland lakes algae can spell trouble for the health of humans and pets. (Cullaby Lake - Oregon Coast Beach Connection)

Oregon Health Authority (OHA) said that as temperatures rise with spring and summer, state health officials are urging Oregonians to be vigilant for harmful cyanobacteria blooms, also known as CyanoHABs, in lakes, rivers, and reservoirs across the region.

While the Pacific Ocean is immune to this, OHA is currently monitoring four Oregon coastal lakes for potential cyanobacteria activity: Devil's Lake in Lincoln City, Siltcoos Lake near Reedsport, Tenmile Lake near Coos Bay and Cullaby Lake at Warrenton.

Monitoring is ongoing all over the state. Several inland lakes are also being observed for potential toxin-producing blooms, including three sites in the Portland metro area, one location near Eugene and multiple lakes across central and eastern Oregon.

When water samples confirm cyanotoxin levels above OHA safety thresholds, the agency issues recreational health advisories. These alerts are disseminated through news releases, social media, email, hotline updates, and the OHA website. Residents are encouraged to sign up for alerts to stay informed throughout the season.

Health Risks and Symptoms

Direct contact with cyanobacteria or their toxins can lead to several adverse health effects. Symptoms may include:
Skin rashes
Diarrhea
Abdominal cramps
Vomiting
Numbness
Dizziness or fainting

Children, individuals with weakened immune systems, and pets are especially susceptible to illness caused by exposure.

Pets Are Particularly Vulnerable

Dogs are at heightened risk due to their body size and water activity. In recent years, multiple canine deaths were reported along the South Umpqua and mainstem Umpqua Rivers after drinking contaminated water. In response, OHA expanded outreach to educate pet owners about the dangers and encourage extra precautions.

Staying Safe Around Fresh Water

Since not all water bodies in Oregon are regularly tested, visual awareness remains crucial. Residents and visitors should avoid water that:
Has an unpleasant odor
Appears scummy, foamy, or thick like paint
Is colored pea-green, blue-green, or reddish-brown

The OHA reminds everyone: when in doubt, stay out.

About Ocean Algae, Phytoplankton

Oregon Coast Beach Connection

In some cases, there are bad algae that can infect seafood like crab, mussels and clams with a biotoxin. This is what causes those sometimes-lengthy closures of shellfish gathering.

However, most of the Oregon coast benefits by massive blooms of microscopic beasties, like diatoms. Especially large blooms up north create brown waves, even oily and sludgy lookings. While this gooey stuff alarms some people and makes them think it's an oil spill, it's actually a healthy thing, according to Seaside Aquarium's Tiffany Boothe.

“While there are harmful algae blooms, diatom blooms are very healthy for the marine environment,” Boothe said.

This actually means our offshore waters are in good shape, if it can support such large amounts of phytoplankton.

“In large concentrations diatoms can also have a very distinct briny marine smell,” Boothe said.

Other kinds of phytoplankton called dinoflagellates create sand that glows.

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