That Wonderful But Weird Thing That Freaks Out People on Oregon Coast: Brown Waves

Published 04/18/21 at 12:05 AM PDT
By Oregon Coast Beach Connection staff

(Oregon Coast) – Periodically, residents and tourists alike get a little spooked by
something found on the Oregon coast: brown waves. They often think it’s something icky, like maybe pollution or an oil spill. In fact, it sometimes resembles either, certainly to the uninitiated.

However, the culprit is a sign of a very healthy ocean: tiny, microscopic creatures called diatoms, which are a form of phytoplankton. You can see these brown waves from the southern Washington coast down through the southern edges of Seaside.

When it happens, more often than not it’s more of a north Oregon coast thing, up around Seaside and northward. It’s not often seen south of there, even more rarely so south of Rockaway Beach.

One inincident in 2010 stands out, however. Its appearance along Lincoln County beaches like Seal Rock, Newport and Depoe Bay caused some residents to call the Oregon Department of Environmental Quality (DEQ) out of concern.

Back then Steve Schnurbusch was with the DEQ office in Salem. He told Oregon Coast Beach Connection some residents feared it might be pollutants from a paper plant up the Yaquina River. His office collected a sample, and analysis under a microscope confirmed it was indeed only this form of phytoplankton.

In Seaside, for a long time tourists often flooded local businesses and tourism entities with questions about the brown stuff, also fearful it’s pollution of some kind. Seaside Aquarium and the city put up signs all over talking about the oddity and the slowly the questions stopped. Certainly the more urgent reports.

(Photo above: brown waves in Long Beach on the Washington coast, courtesy Seaside Aquarium's Tiffany Boothe)

“It’s a good thing,” said Chandler. “It’s a healthy thing. It’s just a lot of diatoms.”

Diatoms are microscopic plant-like creatures that are actually responsible for most all sea foam you see on the beaches. They are about 100 micrometers long – or 1000 times the size of a virus. Still, they’re not visible with the naked eye.

This particular phytoplankton can get so abundant on the north coast that causes really dark patches along with very dark, brown chunks of foam in the Seaside area. Rarely, it happens along the south or central coast, where big chunks of brown foam float lazily along the waves. There, it can create dark, oily-looking patches in the sand as well as large tracts of brown foam and goo along the beaches.

The diatoms thrive off large amounts of nitrates and phosphates, which are extremely heavy in the freshwater runoffs from the Columbia River, Chandler said.

“That’s why it’s so brown here on these beaches," he said. " They’re living off the nitrates and phosphates coming down from the Columbia. That creates these huge blooms of diatoms. They’ve got a lot of stuff to feed off. It’s like gravy to these diatoms. Or like pudding to them.”

Schnurbusch said although it’s rarer on the central coast, given the right conditions it will happen there as well.

Diatoms under a microscope, courtesy Seaside Aquarium

“We’ve got the Yaquina River here, and when it rains heavily you get a lot of the nutrients coming down to spark these enormous blooms,” Schnurbusch said. “Then all you need is a bit of sunshine, which we had as well. These are plants, so they do work on photosynthesis.”

These enormous blooms can bring other surprises.

Often, large blooms of the brown diatoms or the usual diatoms that are responsible for sea foam mean there are other kinds of phytoplankton about. A form of these called dinoflagellates are bioluminescent – creating what is called the “glowing sands” phenomenon. Your chances of seeing these at night on the beaches are greater during these heavy bloom events.

Heavy diatom blooms frequently happen up on the southern Washington coast as the north Oregon coast blooms happen, but not always. If the Long Beach Peninsula has them, chances are pretty good Seaside does.

Those heavy nutrient runoffs from the Columbia also feed the large razor clam population on this part of the northwest coast.

Oregon officials say more than 80 percent of the state’s razor clams are on Clatsop County beaches.

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Photos above and below courtesy Seaside Aquarium. Brown waves have different looks, sometimes more alarming than others

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