Marine Ecosystems Growing Too Hot for Oysters?

Yet another food source supporting the human population at risk.
And many still can't see nature as our support system.
Lance

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"We're in a state of panic," said Robin Downey,
executive director of the Pacific Coast Shellfish
Growers Association, based in Olympia. "There is
no other word for it."
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The Oregonian (Portland, Oregon, US)
Monday, June 09, 2008

Researchers scramble to deal with dying oysters
A bacterium explodes in numbers, killing oyster larvae before they can grow
MICHAEL MILSTEIN

An invisible microbe that thrives in warm ocean
water has undermined the Northwest's prized
oyster supply, killing billions of young larvae
that mature into the succulent shellfish known
across the world.

The bacterium, Vibrio tubiashii, is related to
another species that can sicken people who eat
raw shellfish. This one doesn't bother people --
it kills shellfish in their larval stage, before
they latch onto rocks to grow.


An explosion of the microbe late last summer shut
down an Oregon shellfish hatchery that is one of
the largest on the West Coast, supplying larvae
to about 70 oyster growers the way seed companies
provide crop seed to farmers.

The microbe also is the likely culprit in the
disappearance of recent generations of wild
oysters from usually prolific estuaries such as
Willapa Bay on the southern Washington coast.

"We're in a state of panic," said Robin Downey,
executive director of the Pacific Coast Shellfish
Growers Association, based in Olympia. "There is
no other word for it."

The crisis has the attention of local and state
leaders, including the governor. And scientists
have rushed to devise filters that can strain the
lethal bacterium out of water flowing through
hatcheries.

Researchers say the rise of bacteria might be
tied to the same unusual ocean conditions --
possibly connected to global climate change --
causing the suffocating "dead zones" that have
appeared off the Oregon coast in recent summers.

The bacteria, long known in coastal waters at low
levels, seem to have taken off in the same areas
and about the same times as the dead zones. But
it's unclear what conditions have caused the
bacteria to thrive.

"It's safe to say it's probably all of Oregon and
parts of California and Washington," said Ralph
Elston, a veterinarian with Aquatechnics in
Sequim, Wash., who works with shellfish
hatcheries.

Oysters grow for a few years before they're big
enough to eat, so those showing up in restaurants
now predate the recent bacterial boom that killed
young oysters. Growers predict the loss of those
generations of oysters will shrink supply and
probably drive up prices later this year.

"It's going to have some major effects on the
industry in the next year or so," said Bill
Taylor of Taylor Shellfish Farms, which hatches
and grows oysters on Washington's Hood Canal and
also has been hammered by the bacteria this
spring. "There's not going to be enough
marketable oysters to sell."

Besides oysters, geoducks grown farther north on
the West Coast are at risk. Clams and mussels
seem less vulnerable, though fisheries officials
have noticed a lack of young razor clams along
some areas of the coast.

Hatcheries sound alarm

State biologists don't monitor wild shellfish as
they do key fish species such as salmon.
Shellfish hatcheries, which grow larvae in water
pumped from the ocean, were the first to realize
that young oysters were dying.

"The hatcheries are really the canary in the mine
shaft," said Chris Langdon, a professor at Oregon
State University's Hatfield Marine Science Center
in Newport. "There hasn't been monitoring of this
bacteria on large scales."

West Coast growers produce more than $100 million
worth of commercial shellfish each year, with
oysters by far the largest share. Cultivated
oysters are mainly Pacific oysters, originally
imported from Japan and different from native
West Coast oysters.

But researchers said the bacteria probably also are affecting wild shellfish.

Oyster larvae suddenly disappeared from Willapa
Bay last year, said Alan Trimble, a University of
Washington researcher who works at the bay. He
suspects the bacteria contributed to poor
reproduction of native oysters and razor clams in
bays and coastal beaches.

"When the larvae die in the water column, it
isn't just Pacific oysters; the others disappear
also," he said in an e-mail from Namibia, where
he is on leave.

That could affect the rest of the marine food
chain, because many other forms of marine life
eat young shellfish.

Business shuts down

Late last summer, the bacteria multiplied to
levels that shut down Whiskey Creek Hatchery on
Netarts Bay. Tiny oyster larvae that usually swim
busily under a microscope instead looked shrunken
and feeble as a toxic enzyme secreted by the
bacteria destroyed them, said Sue Cudd, who, with
her husband, Mark Wiegardt, runs the hatchery.

The hatchery usually produces many billions of
oyster larvae each year but couldn't produce any
once the bacteria invaded in August. Wiegardt and
Cudd had nothing to send to growers that depend
on them for their seed stock.

"We have the weight of a lot of people depending
on us," Wiegardt said. "If we don't figure out
this problem, people are going out of business."

The hatchery burned through its reserve funds and
was about to give up. "I had nowhere to go," Cudd
said.

Then the couple found help from the Hatfield
Marine Science Center, which had similar trouble
at its hatchery in 2005. Researchers there
developed a filtration system that uses a
combination of ultraviolet light and other
methods to remove the bacteria from water
entering the hatchery.

Other shellfish growers, many of them the
hatchery's customers, donated money to hire Alan
Barton, a former Hatfield researcher, to design a
similar system at the Whiskey Creek hatchery.

That's now up and running at a cost of about
$180,000, although it handles only enough water
for the hatchery to produce about half its normal
oyster crop of close to 50 million larvae a day.
It will cost an additional $80,000 to expand the
system to provide a full water supply.

"This affects a huge West Coast oyster industry
that goes all the way to the oysters on your
plate," said Mark Labhart, a Tillamook County
commissioner who is trying to help the hatchery
find financial assistance to boost the filter
system.

Finding out why

Concentrations of Vibrio have spiked as high as 1
million in 1 milliliter of water -- at least 100
times usual levels -- and remain higher than
normal, Barton said. The bacterium also took off
in 1998, when an El Nino pattern warmed coastal
waters, though not nearly as severely as it has
recently, Elston said.

He suspects some of the same factors Oregon State
researchers have connected with dead zones along
the coast: strong but intermittent upwelling of
deep water that pushes rich nutrients toward the
surface.

Langdon said the deep water also might be a
source of the oyster-killing bacteria.

Though the deep water is cold, its nutrients
could combine with warm surface waters to nourish
the microbes, Elston said. "The conditions were
just absolutely optimal for a bloom."

The bacteria might now have collected in the
sediments of inlets and bays, and Wiegardt can't
help but wonder what's happening to wild
shellfish in the oceans. "I don't think it's just
about us anymore. It's about what's going on in
the marine environment."

©2008 The Oregonian
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