Can the oyster industry survive ocean acidification?

  • Jeremy Coleman, left, and James Roberts, right, harvest mussels for Taylor Shellfish Farms near Shelton, Washington, in 2011.

    AP Photo/Ted S. Warren
  • Discarded oyster shells at Taylor Shellfish Inc. The hatchery now treats its water to raise pH levels when needed, with mixed results.

    Sarah Gilman

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To stop larvae from munching metaphorical paint chips, Wiegardt and his production manager, Alan Barton, use laptops to monitor the chemistry of water in the bay, and calculate what is known as "aragonite saturation state." Aragonite is a mineral oysters produce using carbonate and calcium in the water that they use to build shells. When they get a reading of 2.0 -- the "magic number" -- or higher, they crank the pumps, flushing the hatchery's tanks with new estuary water. But since the hatchery needs to flush its tanks every 48 hours, that's not enough to solve the problem. When the water falls below the magic number, as it frequently does during summer upwelling periods, they run a series of treatments, which include aerating the water to remove some of the CO2 and injecting it with soda ash to neutralize it -- like using antacids.

Tiny marine plants called phytoplankton, along with eel-grass, assist Barton's doctoring efforts. When the sun is shining, they photosynthesize, sucking CO2 from the water. At night, they release it. So it's better for the hatchery to flush its tanks in the afternoon, once plants have scrubbed some CO2 from the estuary. During severe upwelling episodes, however, the plants are little help.

The careful planning for flushing the tanks and water treatments have helped resurrect Whiskey Creek's production. But cured water is no substitute for the real thing; the hatchery is still only producing 60 to 70 percent of what it once did. "Good water from the ocean is better than good water we produce artificially in the hatchery," says Barton. "We're not that good at it." And in the long term, the windows for pumping good water will shrink because more acidic water will flush the bay more frequently. By mid-century water with aragonite saturations above 1.5 -- lower than Barton's magic number -- will have "largely disappeared," along the West Coast according to a paper published in Science this year.

Whether this will destroy the Pacific Northwest's oyster industry or just change how it operates remains uncertain. But a more acidic sea could impact the survival of oysters beyond the larval stage, which would harm growers who raise the shellfish outdoors where they can't manipulate water chemistry, says Oregon State fisheries professor Chris Langdon. They might be better off farming species that are more resilient to corrosive water, such as clams. Scientists are also experimenting with rearing Pacific Oyster larvae that cope better with more acidic water.

Shellfish farmers may also seek friendlier waters. After struggling to obtain larvae from Whiskey Creek and learning about ocean acidification, Dave Nisbet of Goose Point Oysters in Willapa Bay decided not to gamble on the mercuric local supply. Instead, he built his own hatchery in Keaau, Hawaii, where warmer, saltier water takes up less C02 and is more alkaline. He then ships seed back to Washington, where he rears oysters to adulthood.

Complicating everything is the fact that corrosive water alone can't be blamed for recent slumps. Unlike Whiskey Creek, Taylor Shellfish's hatchery is on a deep bay called Dabob in Washington's Puget Sound. Its water is split into two layers: The upper 60 feet is generally lower in CO2 because sea plants consume it as they photosynthesize; the lower layer is higher in CO2 due to a combination of microbial activity and upwelled water that travels down the Strait of Juan de Fuca, and pours into the bottom of the bay. In summer, northerly winds can bring this water to the surface, creating poor hatchery conditions.  Taylor treats its water as Whiskey Creek does, and has seen some benefit. But the company has suffered even when water chemistry is favorable.  This year, despite chemical conditions similar to last year -- when larval production was robust -- Taylor's numbers are down, and baby oysters are not reaching full size. Production manager Benoit Eudeline suspects it may involve the quality of algae the hatchery raises to feed its baby oysters. "I'm not convinced that at times it's purely high CO2 and low pH," he says. "It has an impact, don't get me wrong, but it's complicated."

To untangle these complicating factors, scientists are studying how bacteria interact with corrosive water to hinder larvae and researching the effects of different chemical conditions on adult oysters used to spawn larvae.

Despite the unknowns, Langdon, the fisheries professor, is optimistic that improved water management at hatcheries and research on more resilient oysters should help the industry cope -- at least in the "near future." What happens after 2050 is a question that remains to be answered.

Michael Lewis
Michael Lewis Subscriber
Dec 10, 2012 07:58 PM
Why are these articles on technical subjects such as ocean pH written by people such as Brendon Bosworth, "an independent South African journalist who’s currently in the U.S... recently finished a master’s degree at the University of Colorado Boulder and am now working as an intern at High Country News?" People who have no experience with the subject at hand, no scientific credentials, no reason why we would accept the conclusions of such an article, obviously lifted from a wire service or press release.

It's time for some journalistic credibility.
Cally Carswell
Cally Carswell Subscriber
Dec 11, 2012 08:07 AM
Hello Michael,

Are there specific aspects of the story you wish to comment on? Otherwise, we ask that you refrain from personal attacks on the authors of HCN stories and other commenters, per our comment policy. This story was thoroughly reported and fact checked with many scientists, a number of whom are quoted in the story. In our view, the fact that Brendon is not a scientist does not compromise his ability to report on this subject matter. In fact, most journalists are not credentialed experts in the subjects they report on.

Cally Carswell
Assistant Editor, High Country News
Joanna Kirkpatrick
Joanna Kirkpatrick
Dec 11, 2012 03:06 PM
The deeper but also more complex question is, can the planet withstand ocean acidification? Think of the consequences to climate and the food chains of ocean as well as earth and air animals that live in and around it.
Jim Vance
Jim Vance
Dec 11, 2012 06:18 PM
It's a basic fact of chemistry and physics that colder water can absorb more CO2 than warmer water (the effect of a cold soft drink not fizzing so much when opened unlike a hot one explosively decompressing), and the CO2 absorbed by the oceans becomes more heavily concentrated in the colder, generally deeper ocean currents. Much is made by climate skeptics or denialists of the limited amount of warming measured by the UK Met, whose HADCRUT models are generally well-accepted as among the current leaders in climatology. A big problem is that the HADCRUT models only incorporate sea surface temperatures to a very limited depth, and not temperatures at lower depths where the heat absorbed from the atmospheric surface interface is being distributed via the Global Conveyor (linked currents) throughout all the planet's oceans. Where these upwellings of cold-current waters exist, the lowering pH trend is becoming well-documented and not simply in Oregon.

Other researchers have begun focusing more attention on the oceanic component of what is essentially a closely-coupled, dynamically interactive atmospheric-oceanic system which comprises the Earth's biosphere, and the findings are in stark contrast to the claim of skeptics (who frequently attempt to argue that acidification isn't a problem either):

Research shows humans are primary cause of global ocean warming over past 50 years[…]/NR-12-06-04.html
ilma Sixthirty
ilma Sixthirty
Dec 17, 2012 07:36 AM
A few slight problems with the article!! Oceans are NOT acidic, they are alkaline. Also, as they absorb CO2, they get MORE alkaline; they can NEVER be acidic. Ocean alkalinity is also temperature dependent, as they cool they absorb CO2, and as they warm the release it.

To say the oceans are corrosive, and that the pH lowers as it absorbs CO2 are just plain factually wrong! Mr. Bosworth needs to take a chemistry lesson.

The use of the term "ocean acidification" is designed to mislead, and the impression is that the oceans are turning to acid and destroying all life. This is so far from the truth, it is beyond comprehension. Using the word "acidification" is like saying "reversing" when slowing down going forwards. "Acidification" is used in the scientific community to mean a direction and not a state, and when used outside of that community, i.e. in public communication such as this, the understanding is the state of "being acid" and not the direction of "becoming less alkaline" or "becoming more neutral". Good journalism should understand this, and phrase accordingly.

This is from a retired scientist...

"Most of the earth's rocks and seabed sediment is essentially CaCO3 (limestone, chalk etc.).

CaCO3 is insoluble in water, but when attacked by acid such as carbonic acid H2CO3 (ie CO2 + H2O) then the following reaction takes place:

CaCO3 + H2CO3 = Ca(HCO3)2 otherwise known as Calcium bicarbonate.

Ca(HCO3)2 is soluble in water and is alkaline (strong base + weak acid = weak alkaline solution).

So the *more* CO2 dissolves in the oceans the more alkaline the oceans are likely to become! In crude terms the oceans are what is called a buffer solution. Ocean pH hovers at around 8 i.e. slightly alkaline.

To summarise. Unless the earth's crust *completely runs out of limestone and other carbonates of Calcium* (and Magnesium; Magnesium Carbonate = dolomite) the oceans can never become acidic.

Local variations can occur of course where there is no limestone present, but even silicate rocks can be slowly attacked by CO2 with a somewhat similar result."

Ms. Carswell, Mr. Lewis was not making a "personal attack", but pointing out, as I have done, that Mr. Bosworth should have undertaken some basic scientific learning before writing such an article, and editors such as yourself should have checked the (so-called) 'facts' for accuracy. To print such an article laden with fundamental errors is either just sloppy journalism, or reveals an pre-disposed bias towards climate alarmism.
Cally Carswell
Cally Carswell Subscriber
Dec 17, 2012 01:15 PM
The story, which focuses on the impacts on a particular region, does not claim the ocean is acidic, but that its pH is slowly declining, a broadly recognized phenomenon widely referred to as "ocean acidification."

Cally Carswell
HCN assistant editor
earl klug
earl klug
Jan 21, 2013 10:00 AM
Ilma (and Michael):
Ocean acidification is not some nebulous phenomena dreamed up by Mr. Bosworth (great article btw); a quick Web search for the term would have revealed scores of entries on the subject, e.g.:

Ilma, I suspect your "scientist" may have retired some time back.