« December 2010 Table of Contents
Going Green: Lethal waters
Pacific oyster growers find themselves 'canaries in a coal mine'
By Lisa Duchene
December 01, 2010
EDITOR'S NOTE: This is the first of two features on ocean
acidification. Look for the follow-up piece in January.
Sue Cudd, owner of Whiskey Creek Shellfish Hatchery on
Netarts Bay in Tillamook, Ore., recalls 2005 as the
normal year for spawning oysters. To produce oyster, mussel and
clam larvae by the millions, Whiskey Creek typically draws 200
gallons of seawater per minute into its hatchery - but can no
longer count on natural seawater.
In late 2007, oyster larvae started dying in huge numbers.
Die-offs continued throughout 2008; Whiskey Creek lost about 75
percent of its production that year. The oysters that survived,
says Cudd, were sub-par.
"Batch after batch after batch with almost no survival,"
recalls Cudd. "We'd lose millions and millions and millions of
larvae. Maybe they'd look like they would make it, but then
they wouldn't. Or, they couldn't develop. Even if they
survived, they'd swim and swim and swim and never grow past 120
In the same period, Taylor Shellfish Farms' hatchery on
Washington's Dabob Bay also lost oyster larvae. In 2008,
Taylor's production was 60 percent below average and in 2009 it
was down 80 percent. All told, the seed shortage translated to
a 22 percent decrease in farmed Pacific oyster production
between 2005 and 2009, according to the Pacific Coast Shellfish
While the two hatcheries, accounting for much of the
region's farmed oyster seed production, are located in places
with different coastal dynamics - Whiskey Creek's facility is
right on the Pacific Coast while Taylor's is nearly 80 miles
from the open ocean, tucked within the Hood Canal estuary, sort
of a fjord within a fjord - they are likely suffering from the
same problem: acidifying sea water.
Simply put: Excess CO2 in the atmosphere drives climate
change while excess CO2 in the oceans drives ocean
Over the past 250 years or so, burning fossil fuels has
increased atmospheric CO2 levels by nearly 40 percent from 280
ppmv (part per million by volume) to 391 ppmv, and the level is
rising by about 2 ppmv per year, according to the European
Project on Ocean Acidification (EPOCA).
During this time, the oceans have been absorbing carbon
dioxide. Otherwise, atmospheric CO2 would be 460 ppmv,
according to EPOCA.
The oceans have absorbed an estimated 525 billion tons, or
about half the fossil fuel carbon emissions, over the last 200
years, according to Richard Feely, senior scientist at the
National Oceanic and Atmospheric Administration's Pacific
Marine Environmental Laboratory in Seattle.
"The ocean's daily uptake of 22 million tons of carbon
dioxide is starting to take its toll on the chemistry of
seawater," writes Feely and colleagues in a briefing paper.
Carbon dioxide absorption lowers ocean pH, which decreases
availability of the calcium carbonate essential to
Scientists have been working to make sense of the
implications for wild and farmed shellfish. Stephanie Talmage
and Christopher Gobler, at Stony Brook University in
Southampton, N.Y., studied the growth and survival of the
larvae of hard clams ( Mercenaria mercenaria ) and Atlantic bay
scallops ( Argopecten irradians ) under past, present and
projected future seawater conditions.
Larvae grown in pre-industrial CO2 concentrations grew
faster and had higher survival rates and thicker, more robust
shells compared with larvae grown under modern CO2 levels.
"Bivalves exposed to CO2 levels expected later this century
had shells that were malformed and eroded," according to the
abstract of Talmage and Gobler's paper, published Oct. 5 in the
Proceedings of the National Academy of Sciences.
The Pacific Northwest oyster industry is likely seeing the
first acute effects of ocean acidification. Along the Pacific
Coast, CO2 levels in seawater traditionally spike due to
upwelling, which varies depending on weather conditions,
explains George Waldbusser, a biological oceanographer at
Oregon State University's College of Oceanic and Atmospheric
Science. North winds affect currents and push surface waters
offshore, allowing deep water to move in.
That water is generally rich in carbon dioxide, accumulated
from sinking, decomposing organic matter. The difference now,
says Waldbusser, is that upwelling is delivering water that
hasn't surfaced in 50 to 75 years and is also enriched with
carbon dioxide from the burning of fossil fuels.
"What's happening," says Waldbusser, "is all of these things
are occurring on daily and seasonal time scales, but in the
background of that you have a general increase in the CO2
that's there. That's what we're concerned about is the shifting
baseline. Essentially, what we're seeing now is the beginning
of the increase in atmospheric CO2. If we
it's a whole lot worse."
By 2009, the Pacific Northwest shellfish industry,
scientists and legislators were working together on the oyster
die-off problem. This year's federal budget included $500,000
to help hatcheries purchase monitoring equipment. In July,
growers, scientists and managers gathered for a workshop on
ocean acidification impacts on shellfish. They concluded that
existing datasets varied too much to explain the impacts of
ocean acidification on shellfish productivity, and that data
collection should be coordinated among all groups.
Taylor's real-time monitoring equipment was installed this
year. Sometimes multiple times a day, the equipment measures
the water's dissolved carbon dioxide, pH, salinity, temperature
and dissolved oxygen. The data picture tells the hatchery when
to spawn the oysters and when not to spawn.
"It's like putting headlights on a car," says Bill Dewey,
director of public policy and communications for Taylor
Shellfish Farms. "All of a sudden, we could see. Before, we
were blindly pumping in seawater and not understanding the
chemistry and not knowing what's going on every time we failed.
Now, with monitoring equipment, we can see the
Says Cudd of Whiskey Creek: "For us, the only thing that is
correlated with mortality is the CO2 level."
Whiskey Creek stops pumping if CO2 levels are too high and
it's working on treating the water to adjust the pH, which
helps but doesn't entirely solve the problem. It is also
experimenting with algae to cleanse the seawater of CO2.
Taylor's hatchery is also closely monitoring the water and
looking to improvements in genetics to adapt. While native
oysters seem to be better adapted to more acidic water,
non-native Pacific oysters are commercially preferred. Among
the Pacifics, some strains are emerging that appear to be more
resilient to the acidity.
Meanwhile, Taylor's 2010 hatchery production was double -
its best year ever. The winds generally blew into Hood Canal
from the south, keeping the surface waters in place and
protecting the hatchery - for now - from water rich in CO2.
Contributing Editor Lisa Duchene lives in Bellefonte,