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coral at coral at
Fri Apr 30 17:00:41 EDT 1999


OCEANSP at CE Issue 134 Friday 30th April 1999
the FREE online marine science and ocean technology magazine

According to studies conducted at Columbia University's Biosphere
2 Center, levels of carbon dioxide, a greenhouse gas found in earth's
atmosphere, have increased since preindustrialized times - primarily
due to the combustion of fossil fuels. Scientific studies have suggested
this trend will continue, resulting in a projected doubling of
atmospheric carbon dioxide levels from preindustrial levels by the
year 2065.

This projected atmospheric change brings with it other potential and
uncertain changes to the earth's atmosphere, biosphere and
hydrosphere. Data collected from large-scale ocean surveys, for
example, have indicated that surface waters of temperate and tropical
oceans are taking up carbon dioxide in proportion to the earth's

Inside Columbia University's Biosphere 2 Center in Oracle, Ariz.,
Lamont-Doherty Earth Observatory Associate Research Scientist
Chris Langdon directly tested and assessed the impact of elevated
atmospheric carbon dioxide on coral reef building and maintenance.
The ocean biome, one of six ecosystems located inside the Bisophere
2 Center, provided an ideal site to study these effects.

Langdon's findings contributed, along with research conducted by
other scientists, to a paper recently published in the journal Science,
titled, "Geochemical consequences of increased atmospheric CO2 on
coral reefs."

The paper suggests that atmospheric changes in carbon dioxide levels
could lead logically to negative changes in reef structure, coral
reproduction and overall function of coral reef communities.

The findings have important global implications, since measurements
of the saturation state of aragonite in surface ocean water show that
it has been decreasing. In the past 100 years, for example, the average
aragonite saturation state in the tropics has dropped about ten percent.
It is predicted this trend will continue, amounting to an average
decrease of about forty percent by the year 2100 from preindustrial
levels. Precipitation, the process by which aragonite and other
calcium carbonate minerals produced by corals solidify into reefs,
also is expected to decrease by 17 to 35 percent from preindustrial
times to 2100.

Reefs that may be the most vulnerable to these changes are those with
balanced calcium carbonate budgets, characterized by rates of growth

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