- WASHINGTON (Reuters) - Carbon dioxide, which is found dissolved in seawater,
could be the death knell for delicate coral reefs, scientists said Thursday.
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- Excess carbon dioxide from burning coal,
gas and other fossil fuels has long been blamed for helping raise global
temperatures through the greenhouse effect, and such higher temperatures
have been blamed for helping kill coral reefs.
-
- Joan Kleypas of the National Center for
Atmospheric Research in Boulder, Colo., and colleagues in France, Australia,
Kansas and California, found that the excess carbon can also dissolve in
the ocean and disrupt complex chemical reactions that the coral uses to
build its reef colonies.
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- "This does not mean the end of reefs,"
Kleypas said in a telephone interview. "It simply indicates that this
could effect some changes in reefs over the next 50 to 100 years. We just
don't know what those effects are yet."
-
- Coral reefs are a cornerstone of ocean
life. Corals are tiny, soft-bodied organisms that form huge colonies that
gradually build up into into rock-like growths as generations of the animals
die and skeletonize.
-
- There is much evidence that coral reefs,
which shelter a huge variety of sea life, are starting to die off all over
the world. Changes in ocean temperatures, pollution, and physical assaults
by boat anchors are all key factors in the decline.
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- But the chemical balance of the sea is
also important, Kleypas's team found.
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- Coral uses carbon in the form of carbonate,
which it combines with calcium to make its skeleton. "It's like the
way we would form bone," said Kleypas, a marine scientist.
-
- "If you think of adding carbon dioxide
to water -- and that's what we are doing (by burning fossil fuels) -- we
are driving more carbon dioxide into the surface of the water, that makes
carbonic acid," she said.
-
- This carbonic acid uses up more of the
carbon that should be available to the coral, depriving it of the carbonate
it needs.
-
- "It's counterintuitive -- you'd
think if you are adding carbon dioxide to water there would be more carbonate
available, but because you are forming an acid you are shifting that carbon
away from the carbonate ion," she said.
-
- The idea first came from amateur aquarium
enthusiasts, who found that when the carbonate balance was off, their coral
changed, she said.
-
- Writing in the journal Science. Kleypas
and colleagues said careful experiments showed this was indeed the case
-- adding carbon changed the way coral grows.
-
- "So far all the data show a good
correlation between how much calcium carbonate there is in the ocean and
how much organisms are laying down in their skeletons," she said.
-
- The effects are not always obvious to
the eye. "Sometimes you can't tell the difference by looking at the
coral," Kleypas said. "But if you weighed two pieces of coral,
one might weigh more than another."
-
- This might, in turn, weaken the coral,
although Kleypas said this has not been demonstrated on a real, living
coral reef yet. "There could be changes out there already but we haven't
gone out to look at those changes," she said.
-
- "I hope we're wrong," she added.
"We really think that the major threats to reefs are still direct
human destruction of reefs and overfishing."
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