美国国家公共电台 NPR Coastal Pacific Oxygen Levels Now Plummet Once A Year（在线收听）

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It's not every day that scientists announce a new season. But that's what ocean researchers just did on the west coast. They say waters off Oregon, Washington and California now have a whole season when the oxygen level on the sea floor drops so low, animals start to die. They call it hypoxia season. Kristian Foden-Vencil of Oregon Public Broadcasting reports.

KRISTIAN FODEN-VENCIL, BYLINE: In Newport Harbor, crab fisherman David Bailey pumps water out of his boat. It's melted ice he needs to replace to keep his catch fresh. He says news of a regular hypoxia season has him rattled. He experienced one a decade ago.

DAVID BAILEY: If there's crabs in the pot, they're dead, straight up. And this will have happened after the time before - everything was fine. And it shows up like a flip of a switch. If you rebait them, when you go out the next time, they're blanks. They're absolutely empty. The crabs have left the area.

FODEN-VENCIL: Fishermen had little notion of hypoxic waters 16 years ago, but they were starting to report the effects. That's when Francis Chan had just finished his Ph.D. and was looking for a research subject.

FRANCIS CHAN: I got a call from Oregon Department of Fish and Wildlife, a biologist there who - he was fielding calls from the fishing industry from crabbers who said, you know, hey. The crabs in my pots are dead.

FODEN-VENCIL: The biologist told him animals that are normally content on the ocean floor were doing strange things.

CHAN: There's octopus - he saw an octopus climbing up the rope, just kind of odd things that fishermen had not seen before. What's happening? What's the problem?

FODEN-VENCIL: He didn't know, but it was a lack of oxygen or hypoxia. It's when ocean water close to the sea floor has such low levels of dissolved oxygen that critters down there, like crabs, sea cucumbers and sea stars, die.

Now there's a hypoxia season that hits the west coast every summer and can last from a couple of days to a few months. It can cover a few square miles or thousands of square miles. And there's even video of it near reefs with dead creatures littering the sea floor. Chan, who is now co-chair of a California hypoxia task force, says the question is, why? Why is this happening?

CHAN: One of the more fundamental reasons is that the ocean is warmer now. And warmer water holds less oxygen. And then the second part is that a warmer surface ocean, it acts as an insulating blanket.

FODEN-VENCIL: Scientists say climate change is behind this. The oceans have been absorbing nearly all the rising heat from greenhouse gas emissions and is projected to grow even warmer in coming decades. Oregon State University oceanographer Jack Barth thinks the higher temperatures are also slowing ocean currents and that if we could see under the waves, there'd be more concern.

JACK BARTH: As an analogy, think about this summer when the skies were filled with smoke - covered the whole Pacific Northwest, right? That's a huge area. When we used to think about hypoxia in the ocean, we'd think about little areas. But now what we're looking at is that out in the ocean, there's low oxygen all along the coast.

FODEN-VENCIL: David Bailey's been crabbing for 40 years. And he says when hypoxic waters showed up, it cost him a thousand dollars or more in lost time and diesel spent sailing around pulling up empty crab pots.

BAILEY: It's a little scary. You know, I've been fishing that many years. The last time I remember it - 10 to 12 years ago - it came up once. And I'd never seen it before. And now there's a season. Something - to me, something's off.

FODEN-VENCIL: The National Oceanic and Atmospheric Administration just issued a grant for about 40 new oxygen sensors to be distributed among crabbers here so they can gather data with their pots. Crabbers say they're happy to hand over the data. But they're not so sure about giving locations. After all, favorite crabbing spots are closely guarded secrets. For NPR News, I'm Kristian Foden-Vencil in Newport, Ore.

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