For the second year in a row, a toxic algae bloom has occurred in the Snake River

Toxic algae are reappearing in the Snake River.

Water samples taken on Aug. 12 showed a large algae bloom near Granite Point, also called Granite Rock, on the Snake River. It's a popular swimming spot about 28 miles from Lewiston, Idaho. Public health officials said it's been especially busy since college and university students returned to campus.

The algae microcystin is a liver toxin that can harm humans, pets and livestock in high concentrations. The toxins can also accumulate in fish. It is the same type of algae that appeared in the Snake River last year.

Health officials in Washington are advising people not to go into waters where green scum is forming on the surface. The scum is forming in several places along a roughly 50-mile stretch of the Snake River between Nisqually John Landing and Little Goose Dam.

The Whitman County Health Department took a baseline sample in June, said Chris Skidmore, the department's director. No toxins were found in those samples, he said.

Ingesting high concentrations can cause liver damage or death. In lower concentrations, health authorities say, it can cause skin irritation.

These blooms often occur when too much water drains into rivers and lakes, Skidmore said.

“When we have heavy rains recently after a very long dry spell, my theory at the moment is that this washes additional nutrients into the water,” he said.

The bloom could last for months. Signs have been put up to warn people, but Miles Johnson, legal director for Columbia Riverkeeper, said a prolonged bloom could close public access to the waterways.

“People should be able to go to the river and swim and take their pets without fear of toxic algal blooms or other toxic pollution,” he said.

One way to reduce the risk of large algal blooms in the Snake River would be to remove the four dams on the lower Snake River, Johnson said.

“There's really something we could do on the lower Snake River for a lot of reasons,” Johnson said, referring to the ongoing debate over removing the four dams. “The dams slow the river down. They make it too hot and they lead to these toxic algal blooms that keep people from using the river.”

Whitman County Health Department leaders said they will continue to monitor water quality weekly and test for toxins at various locations. In addition, Skidmore said satellite photos could help determine the extent of the spill.

“Often you can clearly see the outline of the bloom and how far it extends down the river,” Skidmore said. “That was pretty helpful for us last year.”

To protect themselves, health officials are asking people not to go into waters where an algal bloom is visible. They advise washing skin and clothing if you come into contact with smelly or discolored water. Health officials added that boiling water from an algal bloom will not remove the toxins. Shellfish from waters with algal blooms should not be eaten.