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By Pepper Fisher

PORT ANGELES — Low oxygen levels measured in the waters off the coast of Washington and Oregon are raising concerns of large so-called “dead zones” that could temporarily decimate crab and bottom-dwelling fish populations within them.

Oxygen depletion off our shore, known as hypoxia, happens when summer winds coming down the coast blow surface water out to sea, which brings the deeper water to the surface. That water causes massive blooms of krill and other organisms, who later die and sink to the bottom, where their decomposition causes oxygen depletion. That’s very bad for crabs and, in turn, the local fishery.

But researchers for the National Oceanic and Atmospheric Administration (NOAA) say the problem is, it’s happening more often, covering larger areas, and starting earlier than it used to.

“It is something that we now expect every summer. And it’s true that this year it’s more intense than average and likely bigger in scope throughout the Pacific northwest.”

That’s Dr. Francis Chan, who’s been studying the west coast phenomenon for two decades. He’s just returned from this year’s hypoxia study aboard NOAA’s research ship, the Ronald H. Brown.

He says he first learned about the dead zones from crab fishermen, who reported pulling up pots full of dead crab.

“They said something strange was happening. These are people with decades of experience in the water. We went out, we were able to confirm that, wow, the oxygen levels where you’re crabbing is really low. That’s the culprit, that’s a smoking gun.”

Dr. Chan and his colleagues studied historical records and found that there were no reports from the old-timers of this happening. So what’s changed?

Chan says there’s no question our oceans are warming worldwide, and warmer oceans hold less oxygen.

“The record shows us the water that’s coming to our coast in the Pacific Northwest is lower in oxygen than it used to be. And that really prime’s the system for even more severe, bigger episodes of hypoxia.”

Scientists are getting better at predicting when hypoxia will happen off the northwest coast and its severity. But where exactly the dead zones will be is another story. To learn more about that, Dr. Chan says they’re getting a lot of help from the crab fishermen themselves.

NOAA has given them oxygen sensors they put inside their crab pots, and the data is collected instantly onsite.

“And they are actually on the front lines tracking this phenomenon. We love it because we want information. We want to know where it is, you know, what’s happening out there. So the fisherman are the first to know. They get to know if they’re fishing in a hypoxia zone or not, and then they can decide, you know, should they move to another prospect and another area that might hold higher oxygen.”

To read NOAA’s report on this summer’s study, click here.