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Wednesday, November 26, 2008

Oceans Growing Acidic 10 Times Faster Than Expected

By Dan Shapley

Dead, Eroded Mussels
Eroded mussel shells are possible symptoms of stress from declining ocean pH and increasing acidity.
Photo: C.A. Pfister, University of Chicago

The world's oceans are growing acidic at a rate 10 times as fast as predicted, according to a new University of Chicago study published in the Proceedings of the National Academy of Sciences.

The study also reinforced what we already knew: Ocean acidification results from the same thing that is driving global warming: carbon dioxide emissions. Oceans absorb the lion's share of our pollution, but not without consequence. As the carbon dioxide is absorbed, it forms carbonic acid, which at certain thresholds can prevent marine life from forming calcium carbonate shells. The most likely target will be Arctic plankton that form the basis for the entire food web, but ultimately coral and many other species will be affected, either directly or indirectly through the loss of food.

Further, as oceans become saturated, they may absorb less carbon dioxide, leaving more of it to fill up the atmosphere, where it helps trap the sun's heat near the Earth's surface, fueling global warming.

The new study is based on nearly 25,000 measurements taken over eight years, and amounts to one of the most thorough studies to account for rising acidity. It also documented, on Tatoosh Island in the Pacific Ocean off the coast of Washington, the effects of acidification: The number of mussels and stalked barnacles dropped as acidity increased, while populations of other smaller-shelled and nonshelled creatures increased.

The study adds to a growing list of dire assessments and predictions for the oceans. A recent assessment by a Scripps Institution of Oceanography oceanographer, for instance, predicted that overfishing, acidification, habitat destruction, global warming and nutrient runoff from farming would conspire to drive oceans back toward a primordial state, dominated by the likes of algae and jellyfish.

Original here


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