FILE - Algal bloom found in the Willamette River in Oregon on Oct. 16, 2023. Toxic algae have recently been found on the Snake River between Little Goose Dam and Nisqually John Landing, Wash.
Kristian Foden-Vencil / OPB
Toxic algae is turning up once again on the Snake River.
Water sampling on Aug. 12 revealed a large algal bloom near Granite Point, also known as Granite Rock, on the Snake River. It’s a popular swimming spot roughly 28 miles from Lewiston, Idaho. Public health leaders said it’s been especially busy since college and university students have returned to campus.
The algae, microcystins, is a liver toxin that can harm people, pets and livestock in high concentrations. Toxins can also accumulate in fish. It’s the same type of algae that turned up on the Snake River last year.
Washington state health leaders are advising people to stay out of water that’s got a green scum on the surface. The bloom is popping up in different spots along a roughly 50 mile stretch of the Snake, between Nisqually John Landing and Little Goose Dam.
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The Whitman County Public Health department took a baseline sample in June, said Chris Skidmore, the director for the department. No toxins showed up in those samples, he said.
If ingested in high concentrations, it can cause liver damage or death. In lower concentrations, health leaders said it might irritate skin.
These blooms often happen when there’s too much runoff into rivers and lakes, Skidmore said.
“Recently, when we have these thunderstorm rain events after a very long dry period, my theory right now is that it’s flushing extra nutrients into the water,” he said.
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The bloom could last for months. Signs have been posted to warn people. But Miles Johnson, the legal director for Columbia Riverkeeper, said an ongoing bloom could close public access to waterways.
“People should be able to go to the river and swim and take their pets there without fear of encountering toxic algae blooms or other toxic pollution,” he said.
One way to help decrease the chances for large algal blooms in the Snake River would be to remove the four Lower Snake River dams, Johnson said.
“In the Lower Snake River, there is something real that we could do, for a lot of reasons,” Johnson said, referring to the ongoing debate about removing the four dams. “The dams slow down the river. They make it too hot, and they’re leading to these toxic algae bloom events that prevent people from using the river.”
Whitman County Public Health leaders said it will continue to check water quality each week, testing for toxins in various locations. In addition, Skidmore said, satellite photos could help show the size of the bloom.
“A lot of times you can see a clear outline of that bloom and how far it’s stretching down the river,” Skidmore said. “Last year, it was pretty helpful to us.”
To stay safe, health leaders ask people to not go in water where there is a visible bloom. They said to wash skin and clothing if you come into contact with water that is smelly or discolored. Health leaders added that boiling water from an algal bloom will not remove the toxins. Shellfish should not be eaten from waters with algal blooms.