Trapped in the Dead Zone

Lovers of Pacific salmon and crab have a very personal reason to resent global warming: A “dead zone” of oxygen-depleted water has formed off the coast of Oregon for the sixth year running.

The AP reports that the annual reappearance of the zone portends long-term climate change. At first, the zone’s appearance seems like a good thing for local wildlife:

[T]he Oregon dead zone is triggered by northerly winds, which create an ocean-mixing condition called upwelling.

This brings low-oxygen waters from deep in the ocean close to shore, and spreads nitrogen and other nutrients through the water column, kicking off a population boom of plankton, the tiny plants and animals at the foundation of the ocean food web.

It’s a temporary all-you-can-eat buffet for salmon, which feed on the micro-organisms. But when huge amounts of plankton die, they deplete the ocean of oxygen as they decompose. This year, a submersible camera spotted a “crab graveyard,” and fishermen reported large amounts of rockfish—which can outswim the low-oxygen area’s spread—at the edge of the zone.

Response to the article has been predictably grim. Aaron Weiss, posting on Oregon news station KGW’s Talk of the Town Blog, calls the return
“a summertime sequel for OSU biologists,” and hopefully points out that “the dead zone is a little bit smaller this year.” Well now, THAT is reassuring! On the other hand, Cliff at the enviro-blog Climate Frog compares the Pacific dead zone to the one in the Gulf of Mexico and says, “The impact here is on our supply of food fish, but it’s a climate-related effect that could be seen in other global regions as well.”

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