Monday, December 22, 2008

Ocean deoxygenation

The appearance of large zones of low-oxygen or no-oxygen along exposed outer coasts like Oregon and Washington came as a complete surprise. If someone had told me this rich, diverse, productive ecosystem could rapidly become a ‘dead zone’, I would have thought they were nuts. And yet we’ve seen the seasonal appearance of hypoxia in 6 of the last 6 years. Francis Chan’s close examination of all data on dissolved oxygen from the last 6 decades off the Oregon coast gives a sense of how very bizarre the last 6 years have been. The data show that the normal situation off our coasts is well oxygenated waters, with only 1 of 10,000 records showing any hypoxia. The recent transformation of this ecosystem from one dominated by a diverse assemblage of rockfish, crabs, sea stars, anemones, sea cucumbers, flatfish, lingcod and more to one devoid of life except microbes has been stunning, wholly unexpected and downright scary. We know that many of the fish and some of the crabs seem to be able to swim or scuttle away from the low-oxygen waters, and in some cases they reappear once the levels of oxygen return to normal, but we do not know the long-term consequences of an annual die-off of the habitat-forming, bottom-dwelling species, many of which live to be decades old.
-- Jane Lubchenco

(See also ocean suffocation?)

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