August 11, 2006
Pacific ‘Dead Zone’ Said to Exceed Fears
PORTLAND, Ore. -- Scientists say the oxygen-starved "dead zone" along the Pacific Coast that is causing massive crab and fish die-offs is worse than initially thought.
Scientists say weather, not pollution, appears to be the culprit, and no relief is in sight. However, some say there is no immediate sign yet of long-term damage to the crab fishery.Oregon State University scientists looking for weather changes that could reverse the situation aren't finding them, and they say levels of dissolved oxygen critical to marine life are the lowest since the first dead zone was identified in 2002. It has returned every year.
Strong upwelling winds pushed a low-oxygen pool of deep water toward shore, suffocating marine life, said Jane Lubchenco, a professor of marine biology at OSU.
She said wind changes could help push that water farther out but current forecasts predict the opposite.
After a recent trip to the dead zone and an inspection via camera on a remote-controlled submarine, she said, "We saw a crab graveyard and no fish the entire day."
"Thousands and thousands of dead crab and molts were littering the ocean floor. Many sea stars were dead, and the fish have either left the area or have died and been washed away," she said. "Seeing so much carnage on the video screens was shocking and depressing."
The effect on the commercial fishery isn't yet known, said Hal Weeks, a marine ecologist with the Oregon Department of Fish and Wildlife.
"The last two years have been record-breaking years in Oregon for Dungeness crab" despite dead zones, he said.
"In that fishery there has been no apparent effect. That doesn't mean there won't be," he said.
It is Oregon's most valuable fishery, worth as much as $44 million in recent years.
But Weeks said crab populations fluctuate wildly for reasons not well understood. Whether any harvest decline is a result of normal fluctuation or the effects of the dead zone is hard to say, he said.
He said some reports indicate the loss of fin fish may be due to their movement to areas with more oxygen rather than to mortality.
Al Pazar, chairman of the Oregon Dungeness Crab Commission and a crab fisherman out of Newport, said this season is shaping up to be the second-best ever, around 28 million pounds, but that most crabs are caught in the six or eight weeks following the season's winter opening, well ahead of the appearance of the dead zones.
Few boats are fishing now, he said, and the season closes at midnight Monday. But he said the affected area is a major crab producer, "right in the thick of it."
He said he saw OSU videos from the zone "that made my knees weak."
The 2002 dead zone was the worst until this year's, he said. After 2002, he returned to the area when the season reopened and had good results.
"They do move back in," he said.
Oregon State scientists working with the Oregon Department of Fish and Wildlife used a remote-control device Aug. 8 to check biological impact and continue oxygen sampling.
Dissolved oxygen readings off of Cape Perpetua north of Florence are between 3 percent and 10 percent of levels needed for survival and near zero in some areas.
"Some of the worst conditions are now approaching what we call anoxia, or the absence of oxygen," said Francis Chan, a marine ecologist with Oregon State and the OSU-based Partnership for Interdisciplinary Studies of Coastal Oceans.
"This can lead to a whole different set of chemical reactions," he said. "It's hard to tell just how much mortality, year after year, these systems are going to be able to take."
A reef near Yachats normally swarms with rockfish, but they are gone. Dead Dungeness crab, sea stars and other marine life carpet the ocean floor.
Scientists say water near the bottom is filled with "marine snow," fragments of dead marine life. As it decays, bacteria move in to feed on it and suck remaining oxygen from the water.
"We can't be sure what happened to all the fish, but it's clear they are gone," Lubchenco said.
Similar but lesser zones have been found elsewhere along the Oregon and Washington coasts. Scientists say they don't yet know how widespread it is.
There are no seafood safety issues, OSU experts say. Only live crabs and other fresh seafood are processed for sale.
Researchers say they don't know why it has become an annual event and can't yet tie it to climate change or global warming. The zone this year was spotted about a month ago.
Some dead zones been caused by agricultural runoff. Those similar to Oregon's have been found off of Africa in the Atlantic and Peru in the Pacific.