Acid Oceans Threatening Marine Food Chain, Experts Warn

Scott Norris in San Francisco, California
for National Geographic News
February 17, 2007

The world's oceans are turning acidic due to the buildup of carbon dioxide (CO2) in the atmosphere, and scientists say the effects on marine life will be catastrophic.

In the next 50 to 100 years corrosive seawater will dissolve the shells of tiny marine snails and reduce coral reefs to rubble, the researchers say (coral photos, facts, more).

Four leading marine experts delivered this grim prognosis yesterday at the annual meeting of the American Association for the Advancement of Science in San Francisco, California.

The scientists stressed that increased ocean acidity is one of the gravest dangers posed by the buildup of atmospheric CO2.

"Ocean chemistry is changing to a state that has not occurred for hundreds of thousands of years," said Richard Feely of Seattle's Pacific Marine Environmental Laboratory.

"Shell-building by marine organisms will slow down or stop. Reef-building will decrease or reverse."

Already, Feely said, ocean acidity has increased about 30 percent since industrialization began spurring harmful carbon emissions centuries ago. Unless emissions are reduced from current levels, an increase of 150 percent is predicted by 2100.

Such an increase would make the oceans more acidic than they've been at any time in the last 20 million years, he added.

Sea Creatures' Uncertain Fate

The organisms most directly affected are those that build hard shells or other mineral structures of calcium carbonate. These include numerous species of corals, marine snails, and crust-building algae.

As oceans absorb CO2 from the air, the gas reacts with water to produce carbonic acid. The acid in turn consumes the carbonate that sea creatures need to build their shells.

"This is a problem that no living corals have encountered in their past evolutionary history," said Charlie Veron, of the Australian Institute of Marine Science.

Continued on Next Page >>


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