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Crab and fish dying off in Pacific Northwest coast from ocean "Dead zone"

7/27/06

Seattle, Washington

A "dead zone" of oxygen-poor water has appeared off the Oregon coast for the fifth year in a row, and reports of crab and fish dying off Washington's Pacific shore suggest the phenomenon is occurring here, too.

Members of Washington's Quinault Indian Nation spotted large numbers of dead greenling, rockfish and flatfish on the beach last week. Some live fish were trapped in tide pools, including rat fish - a deep-water species.

"That tells us they were running from something," said Joe Schumacker, of the tribe's fisheries department. "If you're a fish looking for oxygen, the surf zone is where you would want to go."

Dead crab have been reported along the coast in Washington and Oregon by fishermen and observers on shore.

Preliminary data collected by researchers from the Olympic Coast National Marine Sanctuary show low oxygen levels along portions of the state's northern coastline, but it will be a couple of weeks before more complete numbers are in.

"We don't have a full picture yet," said Mary Sue Brancato, resource-protection coordinator for the sanctuary.

With a more extensive monitoring network, researchers at Oregon State University have no doubt a massive dead zone is parked a couple of miles off their state's coast. If northerly winds continue pushing the oxygen-depleted water toward shore, die-offs on par with those of 2002 are possible, OSU marine ecologist Francis Chan said.

That was the first year scientists detected the low-oxygen zone, alerted by widespread reports of suffocating fish and crab.

Since then, dead zones of varying scope and intensity have formed every summer, said OSU marine biologist Jane Lubchenco.

"We think that is signaling a fundamental change in atmospheric conditions," she said.

Shifting winds seem to be the main factor responsible for the dead zones' formation. Those winds are determined by land and sea temperatures - both of which have been rising as a result of global warming.

"We're seeing wild shifts from year to year in the winds that drive this system," Lubchenco said. "This increased variability is exactly what climate change models predict ... but we can't definitively say this is because of climate change."

Dead zones caused primarily by polluted runoff have formed in several marine areas around the world, including the Gulf of Texas and Washington's Hood Canal.

But pollution doesn't appear to play a role off the Pacific coast, Lubchenco said.

What does seem to be key is the wind-driven process of upwelling. Normally considered a good thing, upwelling brings deep, nutrient-rich waters to the shallow ocean, fueling the food web.

But deep waters are naturally low in oxygen, and if the process is knocked slightly askew, the result can be deadly for sea life.

Most of the dead zones off the Oregon coast seem to have been caused mainly by changes in wind patterns, which lead to intense spurts of upwelling, followed by calm periods.

During the calm, tiny plants proliferate madly, then die. Their decomposition robs the water of oxygen.

Washington scientists started taking continuous oxygen readings this year, Brancato said. Before that, spot measurements suggested oxygen depletion but weren't definitive.

"This is the first time we are going to be able to correlate oxygen levels with observational data from crab fishermen and shore-based volunteers," she said.
By Sandi Doughton – Seattle Times

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