US EditionHarmful Algae Bloom Alert Expands to Most of Willamette River Through Portland
The advisory warns people and pets to avoid much of the Willamette River due to toxic algae linked to warm, stagnant waters; two dogs have died this summer, officials said.
- On August 13, 2025, the Oregon Health Authority expanded a harmful algal bloom advisory to include most of the Willamette River through Portland, from Ross Island Lagoon north to Kelley Point Park.
- The advisory followed a cyanobacteria bloom first observed the previous week in the Ross Island Lagoon, a manmade feature created in the 1920s that now fosters stagnant water and warm temperatures contributing to blooms.
- Health officials warned against swimming and high-speed water activities that spray water due to toxin inhalation risks, advising people to avoid water contact near the bloom and not to eat any caught fish.
- Symptoms from exposure include stomach cramping, diarrhea, nausea, vomiting, dizziness, and in pets, seizures and lethargy, with the advisory noting boiling or filtering water will not remove toxins.
- The expanded advisory underscores persistent issues, with advocates urging quicker intervention and financial support to create a waterway across the lagoon embankment to enhance circulation and reduce the frequency of harmful algal blooms.
12 Articles
12 Articles
The Willamette River is Full of Green Algae
There's an advisory for harmful algae throughout most of Portland's stretch of the river. Advocates say state action could prevent algal blooms in the future. by Taylor Griggs This summer, Portlanders have made their way down to the shores of the Willamette River in droves, keen to get the most out of our city's public swimming spot. Now, a harmful algal bloom is putting the fun on pause, at least for a while. The cyanobacteria bloom emerged i…
The Columbian
Annual algae bloom forms on Willamette River. A bill to stop it died in the Oregon House
The thick, green layer of toxin-producing algae currently growing on the Willamette River south of downtown Portland is not just a public health issue but a reminder to Willie Levenson of “a total bur
Harmful algae bloom alert expands to most of Willamette River through Portland
A state advisory warning of a harmful algal bloom expanded Wednesday to include much of the Willamette River running through Portland in what has become a common summer alert in the city.
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