Increasing carbon dioxide threatens coral reefs

May 15, 2000

Researchers at Columbia University's Biosphere 2 Center have determined that increasing levels of carbon dioxide in the Earth's atmosphere may cause more harm to marine coral reef communities than previous research had indicated. Dr. Christopher Langdon of Columbia's Lamont Doherty Earth Observatory and his research team believe that coral growth could be reduced by as much as 40 percent from pre-industrial levels over the next 65 years.

The team found no evidence that reef organisms are able to acclimate after prolonged exposure to the reduced carbonate levels. "This is the first real evidence that increasing atmospheric carbon dioxide levels have a negative impact on a major Earth ecosystem," says Langdon, whose research will be published in the June edition of Global Biogeochemical Cycles, an American Geophysical Union journal that covers global environmental change.

Langdon's team is investigating the impact of changing seawater chemistry on coral reef calcification rates. By mid-century, increasing levels of atmospheric carbon dioxide, caused primarily by the burning of fossil fuels, are expected to reduce by 30 percent the carbonate ion concentration of the surface ocean. When Langdon changed the carbonate concentration in the Biosphere 2 ocean to that projected level, he observed significant reduction in calcification rates for the coral and coralline algae.

Langdon believes the results of his research have some important implications. Coral reefs are natural breakwaters protecting tropical islands and other coastal areas from beach erosion. "While some terrestrial ecosystems may actually benefit from elevated carbon dioxide levels, that does not appear to be the case for shallow marine ecosystems like a coral reef," says Langdon. The impacts are much greater than previously believed, leading to increasing vulnerability of many reefs to other man-caused sources of stress, like over-fishing or pollution, he says.

The project is underway in the ocean ecosystem at Columbia's Biosphere 2 laboratory near Oracle, Arizona. The 700,000-gallon aquarium of artificial seawater with its community of coral reef life mimics key aspects of real world coral reef ecosystems. Biosphere 2 President and Executive Director William Harris says the ability to control precisely the chemical environment and accurately measure changes in the system offers a unique opportunity to conduct research of this kind.
Notes for working press only:

1. The paper, "Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef," will appear in the quarterly journal, Global Biogeochemical Cycles, Vol. 14, no. 2 (June 2000). The authors are Chris Langdon, Taro Takahashi, Colm Sweeney, Dave Chipman, and John Goddard of the Lamont-Doherty Earth Observatory, Palisades, New York; Francesca Marubini, Heather Aceves, and Heidi Barnett of Biosphere 2, Oracle, Arizona; and Marlin J. Atkinson of the Hawaii Institute of Marine Biology, Kaneohe, Hawaii.

2. A copy of this paper (16 pages) may be obtained on request to Harvey Leifert. Include your name, title, publication, address, phone, and fax number, and indicate whether you prefer fax or postal delivery. (Express delivery service is also available: provide name of company, class of service desired, and your account number.)

3. For further information on the science in this paper, you may contact Dr. Langdon at 914-365-8641 or

American Geophysical Union

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