Growing Ocean Acidity May Erode Coastal Ecosystems

May 22, 2008

Ocean waters along North America's west coast are becoming more acidic than expected in response to atmospheric carbon emissions, which will likely cause significant changes to economically vital marine ecosystems, a new study says.

At one spot in northern California, waters acidic enough to corrode seashells now rake the shore, researchers point out.

"The models suggested they wouldn't be corrosive at the surface until sometime during the second half of this century," Richard Feely, a chemical oceanographer with the Pacific Marine Environmental Laboratory in Seattle, Washington, said via email.

Scientists have long known that the oceans serve as a giant carbon sink, moderating the effects of global warming by absorbing about a third to a half of human-caused carbon dioxide (CO2) emissions.

But the added carbon dioxide is lowering the oceans' pH, changing their chemistry and biology, explained Feely, whose lab is run by the National Oceanic and Atmospheric Administration.

Acidic waters inhibit marine organisms from producing the calcium carbonate that makes up their exoskeletons and shells.

"Scientists have also seen a reduced ability of marine algae and free-floating plants and animals to produce protective carbonate shells," Feely said.

For example researchers have seen a decline in swimming mollusks called pteropods that are eaten by creatures ranging from shrimplike krill to whales. The mollusks are particularly vital to juvenile salmon and other commercial fish.

"The impact of ocean acidification on fisheries and coral reef ecosystems could reverberate through the U.S. and global economy," Feely said.

Corrosive Upwelling

Feely and colleagues measured the acidity of waters along the west coast of North America from central Canada to northern Mexico.

They found deep-ocean waters corrosive enough to eat away at seashells and coral reefs are upwelling each spring and summer onto the continental shelf.

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