The Dead Zone

dead-zone-oregon6aug06.gifFew places on earth are more vulnerable to climate change than the oceans. Every passing year provides more and more evidence that serious impacts from human-caused global warming are here now. The San Francisco Chronicle reports:

Peering into the murky depths, Jane Lubchenco searched for sea life, but all she saw were signs of death.

Video images scanned from the seafloor revealed a boneyard of crab skeletons, dead fish and other marine life smothered under a white mat of bacteria. At times, the camera’s unblinking eye revealed nothing – a barren undersea desert in waters renowned for their bounty of Dungeness crabs and fat rockfish.

We couldn’t believe our eyes,” Lubchenco said, recalling her initial impression of the carnage brought about by oxygen-starved waters. “It was so overwhelming and depressing. It appeared that everything that couldn’t swim or scuttle away had died.”

Upon further study, Lubchenco and other marine ecologists at Oregon State University concluded that that the undersea plague appears to be a symptom of global warming. In a study published in the journal Science, the researchers note how these low-oxygen waters have expanded north into Washington and crept south as far as the California state line. And, they appear to be as regular as the tides, a cycle that has repeated itself every summer and fall since 2002.

I will post the link to the Science article below with the abstract. The SF Chronicle explains:

Low-oxygen dead zones, which have doubled in number every decade and exist around the world, have a variety of causes….

Off Oregon, the dead zone appears to form because of changes in atmospheric conditions that create the oceanic river of nutrient-rich waters known as the California Current….

Their productivity comes from wind-driven upwelling of nutrient-rich waters from the deep. When those waters reach the surface and hit sunlight, tiny ocean plants known as phytoplankton bloom, creating food for small fish and shellfish that in turn feed larger marine animals up the food chain.

What’s happening off Oregon, scientists believe, is that as land heats, winds grow stronger and more persistent. Because the winds don’t go slack as they used to do, the upwelling is prolonged, producing a surplus of phytoplankton that isn’t consumed and ultimately dies, drifts to the sea floor and rots….

It’s reasonable to think these hypoxic and anoxic zones will increase as more greenhouse gases build up in the atmosphere.”

The abstract of the Science article, “Emergence of Anoxia in the California Current Large Marine Ecosystem,” (subs. req’d) is:

Eastern boundary current systems are among the world’s most productive large marine ecosystems. Because upwelling currents transport nutrient-rich but oxygen-depleted water onto shallow seas, large expanses of productive continental shelves can be vulnerable to the risk of extreme low-oxygen events. Here, we report the novel rise of water-column shelf anoxia in the northern California Current system, a large marine ecosystem with no previous record of such extreme oxygen deficits. The expansion of anoxia highlights the potential for rapid and discontinuous ecosystem change in productive coastal systems that sustain a major portion of the world’s fisheries.

Not as dramatic as the newspaper article, but a stark warning against inaction nonetheless.


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