Carbon emissions increasing acidity in Alaskan seas

He cannot yet assign a specific average pH value to Alaskan waters, but other data show a clear trend line.

One indicator is the levels of calcium and aragonite. The minerals are fundamental to Alaska's offshore ecosystems. Shell-bearing animals such as king crabs and pteropods – small shell-encrusted creatures that make up the bulk of salmon's diet in the ocean – depend upon calcium carbonate. [Editor's note: Pteropods was misspelled in the original version.]

In undersaturated zones, the calcium- and aragonite-poor water effectively robs those elements from the shells that sea creatures are trying to form. In general, the deeper the layer of saturation, the better for the fish.

Aragonite saturation in the Gulf of Alaska, of which Resurrection Bay is a part, has traditionally extended down to 250 meters, Mathis says. Calcium saturation in the gulf has reached down to about 500 meters, he says. But his data are showing that undersaturated waters are creeping up higher.

"The more man-made carbon dioxide we put into the ocean, the shallower those saturation points will become," says Mathis.

Effects of acidification are not obvious enough to be noticed by a casual observer.

"It's not like you're going to see something washed up on the beach with a dissolved shell," says Bob Foy, director of the National Oceanic and Atmospheric Administration's fisheries research laboratory in Kodiak, Alaska.

The effects of acidification

But his research has found that king crabs raised in incrementally more acidic water grow shells more slowly and have higher mortality rates. What will happen, he suggests, is that animals dependent on calcium carbonate will be more stressed and have greater difficulty with development and reproduction, and might even migrate away. Pteropods are particularly vulnerable, he says. [Editor's note: Pteropods was misspelled in the original version.]

"That's going to impact whole food chains. Maybe it already is. We just don't know," he says.

For commercial fishermen in Alaska, who harvest more than half the nation's seafood catch, the specter of acidification is worrying.

"If you really care about fish – not only to make money but also to eat and feed people – it's of grave concern," says Alan Parks of nearby Homer, who has been fishing commercially for three decades and also works for the environmentally minded Alaska Marine Conservation Council.

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See also:

Agreement on climate change looks unlikely ahead of Copenhagen

Amid charges of global warming hoax, new warning on climate change

Climate change: Are women the solution?

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