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Slate Magazine February 18,
2014
Read the whole story here:
http://www.slate.com/articles/health_and_science/animal_forecast/2013/02/ocean_acidification_and_oysters_shellfish_are_already_suffering_1.single.html
Are Oysters Doomed?
1.2k2750
Don’t believe in climate
change? Talk to a clam
digger.
By Maria Dolan
Behind the counter at
Seattle’s Taylor Shellfish
Market, a brawny guy with a
goatee pries open kumamoto,
virginica, and shigoku oysters as
easily as other men pop beer
cans. David Leck is a national
oyster shucking champion who
opened and plated a dozen of them
in just over a minute (time is
added for broken shells or
mangled meat) at the 2012 Boston
International Oyster Shucking
Competition. You have to be
quick, these days, to keep up
with demand. The oysters here
were grown nearby in
Taylor’s hundred-year-old
beds, but the current hunger for
pedigreed mollusks on the half
shell stretches to raw bars and
markets across the country.
A similar oyster craze swept
the United States in the 1800s,
when the bivalves were eaten with
alacrity in New York, San
Francisco, and anywhere else that
could get them fresh. Development
of a fancy new technology,
canning, meant there was money in
preserved oysters, too. Gold
miners in Northern California
celebrated their riches with an
oyster omelet called hangtown
fry. New Yorkers ate them on the
street; late at night they ate
them in “oyster
cellars.” Walt Whitman had
them for breakfast.
That wave crashed. By the
early 1900s, oysters were
disappearing because of
overharvesting and water
pollution. Today’s revival
is possible because oyster farms
are better managed, and
regulations have improved water
quality. But a modern threat
looms for ice-chilled fruits de
mer platters, although it’s
hard to tell with oyster juice on
your chin. This time it’s a
worldwide problem, affecting
marine ecosystems everywhere.
Ocean waters are turning
corrosive, and it’s
happening so quickly scientists
say there may not be any oysters
left to eat in coming
decades.
Ocean acidification, as
scientists call this pickling of
the seas, is, like climate
change, a result of the enormous
amount of carbon dioxide humans
have pumped into the atmosphere.
Oceans have absorbed about a
quarter of that output, and ocean
chemistry has changed as a
result. Surface water pH has long
been an alkaline 8.2, not far
from the pH of baking soda, but
it now averages about 8.1. That
doesn’t look like much, but
since pH is a logarithmic scale,
that means a 30 percent increase
in the acidity. By the end of
this century, surface water pH
could further lower to 7.8 or
below.
We don’t yet know who the
ocean’s winners and losers
will be in the more corrosive
world. Jellyfish and some
seagrasses may thrive under more
acidic conditions. On the other
hand, calcifiers—organisms
that make calcium carbonate
shells and skeletons, such as
shellfish and corals—appear
to be in trouble. In the United
States, scientists have seen
dissolving clam larvae in Maine,
corroded oysters in Washington
state’s hatcheries, and
mussels with thinned shells off
the Pacific Northwest coast.
Taylor Shellfish first saw
what this pH shift could do to
its business in 2006, when the
company noticed that two- and
three-day-old oyster larvae in
its hatcheries were dying. In
itself, this wasn’t news.
“Hatcheries have a lot of
different variables,” says
Bill Dewey, Taylor’s
spokesperson. “There are a
host of reasons your larvae can
die.” But this time, none of
the usual fixes—filtering
out harmful bacteria, for
instance—made a difference.
By 2009, hatchery production was
down 60 to 80 percent, and others
in the region were reporting
similar problems. Oyster larvae
outside of hatcheries were dying,
too. In Willapa Bay, an estuary
off the southwest Washington
coast where a quarter of the
nation’s oysters are
harvested, many growers rely on
natural sets—free-spawning
larvae that swim around until
they attach themselves to oyster
shells placed by growers. Those
natural sets stopped producing,
and the Willapa growers turned to
the struggling hatcheries for
oyster seed.
The industry finally pulled
out of its tailspin in 2010, when
NOAA scientists determined that
what was killing the oyster
larvae was corrosive water that
entered the hatchery at certain
times of the year—usually in
summer, and specifically on days
when winds from the northwest
caused upwelling of deeper water,
which is more acidic than surface
water. With federal money,
hatcheries were able to install
sophisticated pH monitors and CO2
monitors. When waters are
becoming too corrosive, hatchery
operators can now close off the
seawater intake, and, Dewey says,
“pray that the winds change
soon.”
Monitoring is not a permanent
fix, however, so scientists are
exploring adaptation strategies.
At NOAA’s Northwest
Fisheries Center, research
ecologist Shallin Busch and
colleagues are studying the
possibility of raising oysters in
eelgrass beds, since the plants
naturally take up carbon and bury
it in sediment, perhaps making
their immediate environment less
acidic. In Maine, Mark Green of
St. Joseph’s College is
looking for ways to restore clam
populations by raising alkalinity
in shellfish beds using crushed
shells. “It’s like
putting a layer of Rolaids
down,” he says. Other
possibilities being studied
include lowering pH by adding
sodium carbonate to hatchery
water. Selective breeding may
lead to oysters that survive
better in these new conditions.
Nitrogen runoff from land also
contributes to acidification, so
reducing water pollution can
boost shellfish survival.
Unlike other problems caused
by CO2, ocean acidification is
spurring some action, possibly
because the effects are so
visibly tied to the cause.
“With climate change
there’s often a schism
between scientists and those who
flat out don’t want to
believe it,” says Green.
“It’s hard to get a man
to believe something if his job
depends on not believing
it.” But in this case, he
says, it’s the people in the
industry who are leading
awareness. “Talk to
shellfish clammers—the guys
who dig—and every one of
them is on board, especially the
old timers. They have seen over
the years the populations go from
incredibly productive to
virtually disappearing in many
cases.” One bit of anecdotal
evidence diggers have reported is
clams with thinner shells—so
thin, they say, that sometimes
it’s not possible to fill
bushel baskets to the top because
the fragile shells at the bottom
will be crushed.
For the diggers, a scientific
fix is the only hope they have of
saving their industry. But even
the best near-shore solution
can’t stop the pH drop
that’s taking place
oceanwide, not unless we plan to
stop releasing carbon dioxide
into the atmosphere and replace
it with Milk of Magnesia.
Last fall, some of the first
evidence of how ocean
acidification is affecting
organisms in the wild came from
scientists investigating Southern
Ocean pteropods, tiny marine
snails also known as sea
butterflies. NOAA’s Nina
Bednarsek, lead author of the
report, says the team found
dissolving shells in pteropods at
far shallower depths than
expected. The spiraling shells
were pitted and peeling like
paint on a neglected house.
“It was fascinating and a
bit disturbing to see,” she
says. The dissolution won’t
necessarily kill pteropods,
“but they will definitely be
more vulnerable to predators and
infectious diseases.”
Pteropods are an abundant,
important part of the ocean food
web, preying on the ocean’s
phytoplankton—drifting
plants—and providing food
for larger species. Pteropods
make up 50 percent of the diet of
pink salmon in the North Pacific.
According to NOAA chemical
oceanographer Richard Feely, a 10
percent drop in the production of
pteropods produces a 20 percent
weight drop in a mature pink
salmon. Sea butterflies are an
indicator species, showing that
ocean acidification is already
affecting marine ecosystems.
The long-term projections for
ocean acidification make people
even more anxious. “Even if
we change our CO2 emissions
policies today, the
problem’s going to get worse
in the next 30 to 50 years before
it gets better,” says Dewey,
given how long carbon dioxide
persists in the atmosphere.
“We’re anticipating
that down the road it is probably
going to affect our adult oysters
as well as our
seedlings.”
The corrosive surface water
scientists are measuring is in
effect a time capsule from the
1960s. Carbon dioxide is absorbed
by phytoplankton on the
water’s surface. When those
organisms die, they sink deep
into the ocean, taking the CO2
along for the ride. At depth, the
dead phytoplankton release the
CO2 back into the water. For this
and other reasons, the deeper
ocean tends more toward acidity
than shallow waters. In places
where we are seeing the effects
of ocean acidification first,
such as the northwestern United
States and the parts of the
Southern Ocean studied by
Bednarsek, that old, corrosive
water has risen to the surface.
As the years pass, that upwelling
water will have a lower and lower
pH, reflecting the increase in
our carbon dioxide output from
the 1980s, the 1990s, and today.
By midcentury, it’s likely
that about 50 percent of the
seawater will be too corrosive
for growing oysters.
“It’s like: holy
crap,” says Dewey.
“Seawater conditions are
getting such that they are
dissolving our animals, and the
source of that problem is global
CO2 emissions—what can we
possibly do? Even a big shellfish
company like ours can’t fix
that problem.”
As with climate change, ocean
acidification will require more
comprehensive, aggressive
measures. But, hey, if we
don’t fix this? We’ll
need to invent some new recipes
for jellyfish and seagrass.
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