The mystery of Oregon's 'dead zone'
The area off Cape Perpetua on the central Oregon coast is now a gigantic crab and fish graveyard. It was first discovered in 2002, but according to the Christian Science Monitor, researchers at Oregon State University (OSU) have taken a close-up look into this coastal dead zone. And things are getting worse. A few weeks ago, the researchers measured the level of dissolved oxygen in this part of the ocean. They found that levels were 10 to 30 times lower than normal, down to 0.5 milliliters per liter, a characteristic of hypoxia. And because they have no explanations about this phenomenon, they're even envisioning a total absence of oxygen, or anoxia. But read more...
Here is the -- somewhat dramatic -- introduction of the CSM article.
A half-dozen scientists huddle in a cramped lab aboard the research vessel Elakha, bracing themselves against the rolling swells. As they stare at a pair of TV monitors, images of an aquatic graveyard glide across the screens.
Some 150 feet below, a robotic submersible - looking more like a portable generator with thrusters than a svelte submarine - motors just above the bottom, capturing macabre images of Oregon's newly minted and poorly understood "dead zone."
Below is a photo of Hal Weeks, a researcher with the Oregon Department of Fish and Wildlife, ready to launch the remote operated underwater robot to look at the Oregon's ocean 'dead zone' (Credit: OSU). Here is a link to a larger version.
And the CSM continues to describe the dead area.
The zone is a bottom-hugging layer of water with oxygen levels so low that it can't support the variety of marine life that typically lives in these near-shore coastal waters. The bottom is littered with dead crabs, worms, and starfish. White anemones, brilliant in the submersible's spotlights, look as if they are taking their last gasp. In two runs lasting roughly an hour each, not one fish -- dead or alive -- appears on screen.
Here are more details given by an OSU news release (August 9, 2006).
"We saw a crab graveyard and no fish the entire day," said Jane Lubchenco, the Valley Professor of Marine Biology at OSU. "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. Seeing so much carnage on the video screens was shocking and depressing," she said.
In fact, you can watch lots of frightening videos on this page (search for "Dead Zone Video Footage").
You might wonder where is located this 'dead zone.' Here is a map showing the 'dead zone' areas off the Oregon and Washington coasts where "massive numbers of dead crabs and other sea animals have been noted along with a near complete absence of fish" (Credit: OSU). And here is a link to a larger version.
And what is exactly the level of oxygen found in the area?
Any level of dissolved oxygen below 1.4 milliliters per liter is considered hypoxic for most marine life. In the latest findings from one area off Cape Perpetua on the central Oregon coast, surveys showed 0.5 milliliters per liter in 45 feet of water; 0.08 in 90 feet; and 0.14 at 150 feet depth. These are levels 10-30 times lower than normal. In one extreme measurement, the oxygen level was 0.05, or close to zero. Oxygen levels that low have never before been measured off the U.S. West Coast.
If you know about other ocean areas permanently theatened by anoxia elsewhere in the world, please drop me a note.
Meanwhile, in Oregon and elsewhere in the U.S., researchers are scratching their heads and have no explanations about why this part of the ocean became an hypoxic zone.
Sources: Peter N. Spotts, The Christian Science Monitor, August 25, 2006; and various web sites
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