Toxic Algae Advisories
Cyanobacteria blooms may look like mats floating in the water or stuck on the bottom or the shore. Be on the lookout for waters that look suspicious—foamy, scummy, thick like paint, pea-green, blue-green or brownish red, or bright green cells suspended in the water column.
Not all Oregon waterways are monitored for cyanobacteria. This resource can help you tell the difference between normal algae and toxic algae, but when in doubt, stay out!
Health advisories for toxic algae levels have been issued for the following bodies of water in Oregon and close by waters in Idaho and Washington.
Pets should avoid contact with the affected water. Drinking water directly from areas affected by a bloom is especially dangerous. Toxins cannot be removed by boiling, filtering or treating water with camping-style filters.
- Willow Creek Reservoir in Morrow County 9.19.23
- Brownlee Reservoir in Baker County 7.25.23
Official OHA advisories are lifted when values fall below those that cause human illness. Although the levels detected in these places are below the recreational use values for people, they may continue to be above OHA’s guideline values for dogs. Owners should be aware of the potential exposure to their pets while at these areas, especially shallow, marshy areas where cyanobacteria blooms can form. Cyanobacteria can be present on green algae, growing from the sediment or on rocks. Illness in pets can still occur at lower toxin values, so please continue to exercise caution with pets at these areas:
- Agency Lake in Klamath County LIFTED 11.7.23
- Upper Klamath Lake in Klamath County LIFTED 11.7.23
- Lake Ewauna in Klamath County LIFTED 11.7.23
- Aarons Lake on Sauvie Island in Columbia and Multnomah counties LIFTED 9.14.23
- Hells Canyon Reservoir in Baker County LIFTED 9.27.23
- Willamette River in Multnomah County LIFTED 9.28.23
- Pete’s Slough and Sturgeon Lake on Sauvie Island in Columbia and Multnomah counties LIFTED 8.25.23
- Cullaby Lake in Clatsop County LIFTED 8.21.23
- Galesville Reservoir in Douglas County LIFTED 6.30.23
- South Umpqua River: The advisory covers the South Umpqua River from Canyonville downstream to the confluence with the mainstem Umpqua River, and the mainstem Umpqua River downstream past Elkton to Lawson Bar. Pools in the bedrock along the river's edge are known to develop blooms that can be harmful to pets and people if accidental ingestion occurs. Multiple dog fatalities have resulted from the animals drinking the water and licking toxins from potholes along the riverside.
Children and pets are particularly susceptible to this toxin
Exposure to toxins can produce symptoms of numbness, tingling and dizziness that can lead to difficulty breathing or heart problems and require immediate medical attention. Symptoms of skin irritation, weakness, diarrhea, nausea, cramps and fainting should also receive medical attention if they persist or worsen. Children and pets are particularly susceptible.
Swallowing or inhaling water droplets should be avoided, as well as skin contact with water by humans or animals. Drinking water from these bodies of water is especially dangerous. Oregon Public Health officials advise campers and other visitors that toxins cannot be removed by boiling, filtering or treating the water with camping-style filters.
Oregon Public Health recommends that people who choose to eat fish from waters where algae blooms are present should remove all fat, skin and organs before cooking since toxins are more likely to collect in these tissues.
A hazard for dogs
Dogs have become very sick and even died after swimming in and swallowing water affected by toxic algae. If you find thick, brightly colored foam or scum at a lake, pond or river, don’t let your pet drink or swim in the water. Avoid contact with the water, as toxins can be absorbed through the skin.
Symptoms in dogs
Exposure to toxic blue-green algae can result in:
- Weakness or collapse
- Nausea, vomiting
- Excessive drooling
- Abdominal pain
- Difficulty breathing
- Shaking, trembling
- Tremors, rigidity, paralysis
If your dog goes into the water:
- Don’t let your pet lick its fur.
- Wash your pet with clean water as soon as possible.
- If your dog has symptoms such as drooling, weakness, vomiting, staggering and convulsions after being in water, seek immediate veterinary care. Acute, life-threatening symptoms from cyanobacterial toxins often develop rapidly. Death can occur within minutes to hours after exposure.
For more information, contact the Harmful Algae Bloom Surveillance program at (971) 673-0400.
Updated: November 9, 2023