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How does carbon dioxide affect ocean life?

Shell of live Clio pyramidata pteropod mollusk collected from the subarctic Pacific. Image courtesy of Dr. Victoria J. Fabry.
Click here for a high resolution photograph.

As human activities like driving have pumped carbon dioxide into the air, the oceans have absorbed a large portion of this gas. Richard Feely of the National Oceanic and Atmospheric Administration and his colleagues wanted to know what the effects might be on certain ocean animals that are sensitive to the chemistry of the water they live in.

Many mollusks, corals, and single-celled creatures called foraminifera and coccolithophorids use ingredients in seawater to build their shells and other hard parts. Specifically, they pull "carbonate" ions out of the water and make a hard material called "calcium carbonate."

As you might guess from the name, carbon plays an important role in the chemical reactions that allow these animals to make their homes. But, if the amount of carbon dioxide in the seawater increases above a certain level, these conditions lead to a different set of reactions that don't produce carbonate ions.

NOAA ship Ronald H. Brown, and other NSF ships, were utilized to acquire the global carbion dioxide survey data used to determine the effects of anthropogenic carbion dioxide on calcium carbonate systems in the oceans. Image courtesy of Richard A. Feely.
Click here for a high resolution photograph.

In parts of the ocean that don't have enough carbonate ions, calcium carbonate shells start to dissolve.

Feely's research team used new ocean chemistry measurements to estimate how fast calcium carbonate is dissolving in the world's oceans. In the 16 July 2004 issue of the journal Science, the researchers predict that if carbon dioxide emissions continue to increase, ocean areas where these animals have trouble building their homes could expand.

This trend would probably begin with colder surface waters at higher latitudes, which might mean that the mollusks and other shell-forming animals living there would have to move to lower latitudes. If the trend continued, the areas where calcium carbonate dissolves could keep moving closer to the equator, the researchers say.

These predictions don't necessarily have to come true. If humans can change our activities so that we don't put so much carbon dioxide in the atmosphere, then we might be able to modify our impact on ocean chemistry.


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