TIGARD -- The Tualatin River is safe for recreational use again, now that potentially toxic algae mats have been swept away by the river's natural flow, said Stewart Rounds, a spokesman for the U.S. Geological Survey.
The state health department had issued a public health advisory July 12 about the river's algae mats and their potential toxicity.
According to tests conducted July 16, the Tualatin River now has a normal and manageable population of blue-green algae anabaena, which can release toxins after it dies.
"Anabaena is still in the river, you can't really say that this stuff is absent," he said. "Small amounts of it will always be in the river during the summer."
Currently, algae levels are safely within legal Oregon limits, he said.
"(The river) should be fine for the normal types of uses that it gets, as long as people aren't swimming where there are visible floating mats of algae," Rounds said. "Much more commonly, people use the Tualatin River for canoeing or kayaking, and it should be safe for that."
Blue-green anabaena releases anatoxins, which affects the nervous system, and microcystin, a liver toxin. Algae mats do not usually congeal in bodies of water with a current, Rounds said, making them rare in rivers.
Rounds said the return of potentially toxic algae is "possible, but hopefully unlikely."
-- Sarah Dunlap; email@example.com