Ocean acidification threatens Bering Sea crabs. But can they adapt?

Ocean acidification could threaten some of Alaska’s most important fisheries. Researchers warn that populations of red king crab in the Bering Sea – made famous by the show The Deadliest Catch – could collapse by the end of the century.

But it’s possible the crabs might be able to evolve and adapt to the changing oceans. The big question is – will they have enough time?

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Biologist Robert Foy reaches into a tank in his Kodiak lab, as about 20 red king crabs move around on the bottom. They are giant. They are spiny. They are kind of terrifying. But not to Foy. He scoops one out by the back leg.

“As long as you stay away from the first two, the pincers, you’re just fine,” Foy said.

Foy directs the Alaska Fisheries Science Center’s Kodiak Laboratory. His seawater lab is wall-to-wall crabs, in tanks and re-purposed containers: baby tanner crabs no bigger than a quarter and adult king crabs the size of my torso; crabs in tupperware, crabs in laundry baskets, crabs stacked in what Foy calls the “crab condominium.” A tangle of pipes and wires feed seawater into the different tanks, each one carefully calibrated by temperature and pH.

This lab offers a peek into the future. The tanks represent the oceans around Alaska decades from now. And Foy says that future is alarming.

“The expectation in change in pH over the next five decades in Alaska is fairly dramatic,” Foy said.

The change in pH is a measure of how acidic the ocean is becoming. In simple terms, the more carbon dioxide is dissolved in the water, the more acidic it becomes.

Ocean acidification is the less-well-understood fellow-traveler to climate change, the other impact of pumping CO2 into the atmosphere. And like climate change, it’s expected to happen faster at high latitudes — like the waters around Alaska — than in the rest of the world.

Foy began this work about a decade ago, and his lab has been able to run long-term experiments, over years. It’s some of the first concrete evidence we have of what ocean acidification might mean for marine species.

And Foy’s first results are discouraging – at least for red king crabs. Under conditions similar to what researchers are eventually predicting for Alaska, pretty much all the young red king crabs died.

“If the results in the laboratory are accurate, and there’s no acclimation, you would see stock failure about 100 years from now,” Foy said.

That’s in part because it’s harder for many crabs to make and maintain shells in more acidic water: the chemistry isn’t right. But Foy’s team found that a bigger problem may be the sheer energy required for crabs to keep their internal pH right, when the external pH is wrong.

In very acidic water, most red king crabs didn’t make it past their early life stages.

But some did. And that’s giving researchers like Foy hope. Because if the survivors have some trait, something in their genetic make-up that helps them cope with more acidic waters, it’s possible they could pass that on to their offspring and the species could evolve.

But with oceans changing so fast – is there time for that?

“That’s the question,” Foy said. “Even if they could acclimate in a short period of time, or even adapt over a longer period of time, what kind of abilities will they have to do that physiologically if it happens over the scale of 50 years? That’s only a handful of generations for a crab species.”

This question is something crab fishermen are very aware of.

Edward Poulsen is a partner on two Bering Sea crab vessels. He grew up in the industry; he says his dad was one of its pioneers.

“It’s one of those things where you don’t want to think about it too much,” Poulsen said. “Because if you think about it too much, it’s pretty depressing.”

Poulsen knows the science. So do his fellow vessel-owners. He says everyone is concerned. But the potential problems are far enough in the future, and it’s not clear there’s anything fishermen can do about it.

“A lot of us, this is all we know, this is what we do,” Poulsen said. “And now the government’s telling us, ‘Your future might be at risk.’ I think it’s a little bit like you want to put your head in the sand and ignore what could be coming down the path.”

Poulsen says fishermen basically have two choices: they can try to diversify their business, and branch out into other fisheries.

Or they can hope the crabs adapt.