Cyanobacteria Harmful Algae Bloom Advisories: Wapato Marsh at Oaks Bottom Wildlife Refuge

Also known as toxic algae, cyanobacteria harmful algae blooms can cause serious illness or death in pets and livestock that ingest water or mats containing high concentrations of cyanotoxins. Dogs can get extremely ill, and even die, within minutes to hours of exposure to cyanotoxins from drinking water, licking their wet fur or eating floating mats or dried crust along the shore. 

What to Watch For

A toxic algae bloom can look foamy, scummy, thick like paint, and pea-green or blue-green in color. It can look like a thick green or brownish-red mat, or bright green clumps suspended in the water. If you find thick, brightly colored foam, scum or mats in a lake, pond, river or stream—especially in shallow, marshy areas where cyanobacteria blooms can form—don’t let your pet drink or swim in the water. 

Owners should be aware of the potential exposure to their pets while at these areas. Toxins cannot be removed by boiling, filtering or treating water with camping-style filters. This resource can help you tell the difference between normal algae and toxic algae, but when in doubt, stay out!

Active Advisories

Reminder: Not all Oregon waterways are monitored for cyanobacteria. 

Starting in 2025, Oregon Health Authority will issue pre-emptive public warnings following reports of dog illnesses or deaths possibly resulting from cyanotoxin exposure. 

• Wapato Marsh at Oaks Bottom Wildlife Refuge in Multnomah County 5.1.25

Permanent Advisory

• 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 Sawyers Rapids. Pools in the bedrock along the rivers edge are known to develop cyanobacteria (blue-green algae) blooms that can be harmful to pets and people if accidental ingestion occurs.

Lifted Advisories

Illness in pets can still occur at lower toxin values, so please continue to exercise caution with pets at these areas:

• Emigrant Lake in Jackson County LIFTED 5.9.25

Advisories in Surrounding States

• California
• Idaho
• Nevada
• Washington

Children and Pets are Particularly Susceptible

The most common toxins in harmful algal blooms in Oregon are microcystins and cylindrospermopsin. Exposure to these 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 affected bodies of water is especially dangerous. 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.

Symptoms in Dogs

Exposure to toxic blue-green algae can result in:

• Weakness or collapse
• Nausea, vomiting
• Excessive drooling
• Weakness, fatigue, stumbling
• Abdominal pain
• Diarrhea
• Difficulty breathing
• Shaking, trembling
• Seizure like activity—tremors, rigidity, paralysis
• Liver failure

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.