Oceans Becoming Acidic Ten Times Faster Than Thought

Helen Scales
for National Geographic News
November 24, 2008

Increasing levels of carbon dioxide in the atmosphere may make Earth's oceans more acidic faster than previously thought—unbalancing ecosystems in the process, a new study says.

Since 2000, scientists have measured the acidity of seawater around Tatoosh Island off the coast of Washington state. The acidity increased ten times quicker than climate models predicted.

The research also revealed the corrosive effect of acidic oceans could trigger a dramatic shift in coastal species and jeopardize shellfish stocks.

"The increase in acidity we saw during our study was about the same magnitude as we expect over the course of the next century," said study co-author Timothy Wootton, a marine biologist from the University of Chicago.

"This raises a warning flag that the oceans may be changing faster than people think," he said.

Increased carbon dioxide emissions from human activities have led to a 30 percent rise in ocean acidity in the past 200 years.

(Related: "Acid Oceans Threatening Marine Food Chain, Experts Warn" [February 17, 2007].)

When atmospheric carbon dioxide dissolves in the oceans it forms carbonic acid, which in turn has a negative impact on marine life.

Laboratory studies show that as seawater acidity increases, the calcium carbonate shells and skeletons of many marine species, such as hard corals, sea urchins, and stony seaweeds, begin to corrode.

A Shifting Balance

Wootton and colleagues built models of an ecosystem based on field data of how species interact along Tatoosh Island's rocky shores.

Surprisingly, in a scenario of increasing acidity, not all species with calcium carbonate shells faired badly.

Continued on Next Page >>


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