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'Dead zone' returns to Oregon coast for sixth year

7/31/2007

GRANTS PASS, Ore. — The return of oxygen-depleted water off
the Oregon coast is a sign of a warming climate, which could have
ill effect on populations of sea creatures, scientists said Monday.

It's the sixth year the water, known as a dead zone, has formed.

"It does, indeed, appear to be the new normal,'' said Jane
Lubchenco, professor of marine biology at Oregon State University.
"The fact that we are seeing six in a row now tells us that
something pretty fundamental has changed about conditions off of
our coast.''

Unlike the dead zone in the Gulf of Mexico, which is caused by
fertilizer washing down the Mississippi River, the Oregon dead zone
is triggered by northerly winds, which create an ocean-mixing
condition called upwelling.

This brings low-oxygen waters from deep in the ocean close to
shore, and spreads nitrogen and other nutrients through the water
column, kicking off a population boom of plankton, the tiny plants
and animals at the foundation of the ocean food web.

Normally, this is good for salmon, giving them lots of food to
eat. But when huge amounts of plankton die, they fall to the bottom
of the ocean, where they decompose, depleting the water of oxygen.

Oregon State researchers found conditions returning during a
survey of the 25 miles of continental shelf between Newport and
Cape Perpetua last Friday.

Instruments towed back and forth from one mile offshore to 12
miles offshore found oxygen levels as low as one-sixth of normal,
said Francis Chan, a research professor of marine ecology.

That is not as bad as last year, when scientists plotted a dead
zone that stretched from southern Oregon to the tip of Olympic
Peninsula in Washington, a distance of nearly 300 miles.

Video from a remotely operated submersible showed a crab
graveyard on the Perpetua Reef south of Newport, and fishermen
reported unusually large numbers of rockfish — apparently able to
swim away from the dead zone — in unexpected areas on its edges,
Lubchenco said.

New video from May showed that some rockfish and sea stars had
returned, but that less mobile creatures such as sea anemones and
sea cucumbers had not.

"The current low oxygen conditions may knock the system back to
the starting line, delivering another setback to an already
stressed system,'' Lubchenco said. "This marine ecosystem may take
as long to recover as the terrestrial ecosystem did from the
eruption of Mount St. Helens.''