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Collection: Northwest Ocean Acidification

Trouble on the Half Shell

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gautsch.net, flickr

Four summers ago, Sue Cudd couldn’t keep a baby oyster alive.

She’d start with hundreds of millions of oyster larvae in the tanks at the Whiskey Creek Shellfish Hatchery in Netarts, Oregon. Only a handful would make it.

Sometimes, they’d swim for a couple of weeks. But they’d stop developing before they grew a critical shell structure, or maybe the foot or eyespot. They’d feed poorly. One day, the larvae would simply die. A hatchery that has supplied seafood businesses for three decades had virtually nothing to sell for months, said Cudd, who owns the hatchery.

They would just sort of fade away…It was really devastating. We’re kind of the independent growers’ hatchery, and we had always been reliable up until that point. People were just shocked. I heard a lot of times how it was ruining people’s businesses.

It’s tough to say with scientific certainty that ocean acidification is the sole cause of the die-offs that have plagued two of the Northwest’s three major oyster hatcheries in the last few years.

But this much seems clear: young oysters have a hard time surviving in conditions that will only become more widespread as carbon dioxide from cars, coal plants and other industries cause the fundamental chemistry of the ocean to become more acidic. (For more on that process, see our earlier posts here, here and here).

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The Puget Sound Shuffle

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Inside a cramped Seattle laboratory, the researchers look like fishermen who got sent to a construction job. Wearing orange waders and yellow boots, they thread their way between shelves of tubs filled with what look like giant mason jars.

Overhead, a rainbow of colored tubes bubble gases into tanks, changing the water chemistry to reflect different points in time—past, present and future—as increasing amounts of fossil fuel pollution make the oceans more acidic.

If it’s possible to predict how this process of ocean acidification will affect the Northwest’s marine life, this is where it will happen. Over the next months, the scientists will run experiments on some of the region’s most valuable marine species: geoducks, Pacific and Olympia oysters, pinto abalone, rockfish, crab and tiny shrimp like krill and copepods that are linchpins of the food chain.

They’ll immerse those creatures in baths of acidified seawater and assess their most basic biological functions: how big do they get, can they grow shells, are they developing normally, are they more stressed, do they succumb to disease. And most importantly, do they survive?

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Coming to a Shore Near You

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Five years ago, many scientists probably thought they’d never see large pools of corrosive water near the ocean’s surface in their lifetimes.

Basic chemistry told them that as the oceans absorbed more carbon dioxide pollution from cars and smokestacks and industrial processes, seawater would become more acidic. Eventually, the oceans could become corrosive enough to kill vulnerable forms of sea life like corals and shellfish and plankton.

continental shelf clip artBut scientists believed the effects of this chemical process—called ocean acidification—would be confined to deep offshore ocean waters for some time. Models projected it would take decades before corrosive waters reached the shallow continental shelf off the Pacific Coast, where an abundance of sea life lives.

Until a group of oceanographers started hunting for it.

“What we found, of course, was that it was everywhere we looked,” said Richard Feely, an oceanographer at the National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory in Seattle, who was one of the first to recognize the trouble ahead.

The researchers found surprisingly acidic water—corrosive enough to begin dissolving the shells and skeletal structures of some marine creatures—at relatively shallow depths all along the West Coast, from British Columbia to the tip of Baja California. Researchers hadn’t expected to see that extent of ocean acidification until the middle to the end of this century. But in a seasonal process called “upwelling,” summertime winds pushed surface waters offshore and pulled deeper, more acidic water towards the continental shelf, shorelines, and beaches.

Or, as one Oregon State University marine ecologist put it: “The future of ocean acidification is already here off the Oregon Coast.

 

Acidifying water poses a threat to marine animals, especially ones that need calcium carbonate to build shells and skeletons. In the Northwest, that includes everything from geoducks, a giant clam that supports one of the region’s most valuable commercial fisheries, to krill, the tiny shrimplike creatures that give salmon flesh its distinctive pink color and feed rockfish, seals, and whales.

Other effects of low pH water on marine creatures range from lethal to bizarre to beneficial. In laboratory studies, clownfish exposed to more acidic seawater have lost their sense of smell and ability to find habitat, Antarctic krill embryos failed to hatch, northern abalone larvae from British Columbia died, squid didn’t want to move, and some eelgrass grew more abundantly.

Hood Canal-flickr-MiKThen, the oceanographers announced another startling discovery last summer. On the surface of Puget Sound, they found waters with a pH of 7.7, roughly on par with the most acidified waters found in the earlier study along the West Coast.  In the deeper waters of southern Hood Canal, the acidity level was even higher—the pH plummeted to 7.4.

It was some of the most corrosive seawater recorded anywhere on Earth.

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The Acid Test

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ocean flickr Rik_CEvery day, the oceans do us a huge favor. Across the planet, they absorb nearly one million metric tons of carbon dioxide each hour, removing about a third of the greenhouse gases from the atmosphere that would otherwise speed up global warming. This seems, at first, to be a massively beneficial service.

But the oceans haven’t been able to soak up the extra carbon pollution without a cost.

The basic chemistry is simple: as oceans absorb more carbon dioxide, they become increasingly acidic and potentially harmful to a wide swath of sea life, from giant clams to tiny plankton that play a role in the diets of most things you might see at a local aquarium. Many of those species wind up on fishing boats, processing plants and dinner plates around the world.

fishing boat flickr chetWillMarine life—from clams to king crab, sea urchins to salmon—has supported the Northwest and its inhabitants for centuries. But a mix of ocean currents and chemistry has put local waters on the leading edge of ocean acidification, a phenomenon that could produce profound changes to the marine food web and industries built upon it.

Here’s how Terrie Klinger, an associate professor at the University of Washington’s School of Marine and Environmental Affairs, described in a Congressional hearing the uncertainties and possible effects of ocean acidification:

We won’t see a total collapse of the food chains, but we will see substitutions…We may end up with food chains or food webs that are highly undesirable and not productive for the means that we use them today.

sea star flickr loreThere’s a lot riding on how marine creatures will adapt to acidifying oceans. The animals that dissolve in more corrosive seawater range from oysters, a bedrock species in the Northwest’s lucrative commercial shellfish industry, to krill and pteropods, tiny sea snails propelled by wing-like feet that make up more than half of the diet of some young Alaska pink salmon. A recent study found that larvae of British Columbia’s northern abalone died or grew abnormally in more acidic water, offering some of the first direct experimental evidence that changing sea water chemistry is negatively affecting an endangered species.

And here are two pertinent pieces of news for anyone living in the Northwest.

  1. Surprisingly corrosive waters have already been found off our shores.
  2. It surfaced decades before scientists expected to see it.

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