What’s With the Mileslong UO-Green Algae Streak in the Willamette River?

As a proud orange-and-black Beaver, I have to ask: What’s with the mileslong UO-green algae streak in the good old Willamette? Has the river started doing recruitment for the Ducks? —Jay H.

My first thought upon seeing the phenomenon you describe, Jay, was that I’d somehow wound up in Chicago on St. Patrick’s Day—an epic blackout even by my standards. After a closer look, however, I realized that slimy pond scum, green though it may be, is probably not the river-dyeing agent Chicagoans would choose to symbolize their heritage. Unless someone created a St. Donald’s Day when I wasn’t looking, the stain on our river is a natural phenomenon.

Spotting an algae bloom on the Willamette would not be a big deal except for two things: First, sometimes algae blooms are toxic and, second, the middle of a not especially warm October is pretty late in the year for a bloom to crop up.

The unusual timing may have interested scientists at Oregon’s Department of Environmental Quality, who were on the river Monday collecting samples for analysis. The worry was that this material might have been cyanobacteria, the organism that puts the “toxic” in “toxic algae bloom.” Fortunately, they found that this particular bloom was not dangerous—in fact, it’s not even algae, but the water fern Azolla.

Cyanobacteria, or blue-green algae, really do secrete exotic toxins that under the right circumstances will totally kill your dog, so it’s wise to be cautious. Then again, lots of the algae you see is plain old green algae you don’t need to worry about. Can you just look at the color and comport yourself accordingly?

Well, no. Annoyingly, not all blue-green algae are blue-green. Some are just green, others are white, brown, red or even purple. Experts can (sometimes) distinguish the toxic from the benign by sight, but the rest of us will have to keep checking cyanobacteria advisories.

But don’t hate on cyanobacteria too much—in a way, they’re kindred spirits to humanity. You see, 2.4 billion years ago, they invented oxygenic photosynthesis, releasing oxygen as a byproduct. Good news for us oxygen-breathers! Unfortunately, other species at the time found free oxygen toxic and, as it built up in the ancient atmosphere, most of them went extinct.

We now call this event the Oxygen Catastrophe, and it was the first time a species caused a mass extinction solely by polluting the atmosphere with the waste from its own activity. Bet it won’t be the last, though!

Questions? Send them to dr.know@wweek.com.