Oysters May Foreshadow Acidic Oceans’ Effects

Research on local oysters sheds light on how animals will adapt to ocean acidification

Bodega Marine Lab / UC Davis

Scientists from UC Davis are studying oysters and mussels to figure out if organisms will be able to adapt to climate change.

This week, scientists from around the world are meeting in Monterey to discuss what they call the “other” climate change problem: the oceans are becoming more acidic. It happens as oceans absorb the carbon dioxide we add to the air through burning fossil fuels. It can be bad news for oysters, mussels and the marine food web. How bad? Scientists are hoping that ocean conditions off the California coast will help them find out.

At the Hog Island Oyster Company, near Point Reyes, Terry Sawyer orders oysters from hatcheries in Oregon and Washington when they’re small. They grow up in big mesh bags that sit out in Tomales Bay, where they get plump in the cold waters of the Pacific.

But a few years ago, Sawyer started getting calls from those suppliers. They couldn’t fill his orders.

“They would have tens of thousands of gallons of tanks that were absolutely full of larvae. They would have the entire system die or crash,” he says.

The hatcheries were filling their tanks with seawater that was becoming more acidic. Scientists say the oceans are 30% more acidic since the start of the Industrial Revolution. The more acidic the water, the harder it is for animals like oysters to develop their shells.

Sawyer is growing his own oyster larvae now so he’ll have a more predictable supply. But he says there’s no question that climate change is affecting his bottom line.

“We don’t know if we’re going to be able to survive the very real trending that is going on out there,” he says.

It’s trend that could affect the entire food web.

On a rocky point an hour drive north of Point Reyes, a team of scientists from the University of California’s Bodega Marine Lab is gathering. The rocks are covered in tightly packed, purplish mussels – what ecologist Eric Sanford calls the “foundation species” of the California coast.

“One that really defines the whole ecosystem, sort of the way corals define a coral reef,” he says.

Mussels are a key part of the food web. And so are a lot of animals with shells.

“Probably most people like the fact that we have things like whales and salmon off our coast and those organisms are likely to be impacted because their food source will be impacted,” says oceanographer Tessa Hill.

So the big question is: Will animals with shells be able to adapt to a more acidic future – where, in a hundred years, the oceans could be more than twice as acidic?

These California mussels could help answer that.

“They’re facing the most acidic water that you’d see in the ocean today,” says Hill.

“The trouble is right now, the rate at which the ocean is acidifying is way faster than it ever has before.”

Acidic water from the deep ocean rises to the surface on the West Coast in the spring and summer, when the wind is blowing. This upwelling makes the waters off California some of the most acidic in the world.

Inside their lab, Hill and Sanford show me jars full of young mussels, almost too small to see. Each jar is from a different part of the West Coast – from Oregon to Santa Barbara. They’re being grown in more acidic water to see if they’re better adapted to handle it, according to Sanford.

“So this is the issue we’re looking at is whether there might be genetic differences among different populations along the coast in their ability to cope with ocean acidification,” he says.

Steve Palumbi is a biology professor at Stanford University who is also working on the project. He looked at the genes of another shelled animal on the West Coast – sea urchins.

“We found they have lucky genes,” he says.

You can think of genes like a set of tools, Palumbi explains.

“If you happen to have bad plumbing, you will have more plumbing tools in your house.”

And there have been lots of plumbing problems on the West Coast – lots of acidic water.

“And so all these populations, urchins anyway, have had to get the tool set to deal with it,” he says.

Palumbi says in some urchins, they found around 100 genes that make them better adapted to more acidic water. That makes them more likely to survive and reproduce.

“This is good news because these organisms have the capacity to deal with more acidification,” he says. “But it’s not good news forever because all it does is give us a little breathing room. The trouble is right now, the rate at which the ocean is acidifying is way faster than it ever has before.”

Organisms will evolve, he says, but probably not fast enough to keep up. In the meantime, Palumbi and other scientists are mapping where the genetically resilient mussels and urchins are on the West Coast, so policymakers can look at protecting them.