Monday, November 12, 2007

Oceans could absorb far more CO2, says study

PARIS (AFP) - The ocean's plankton can suck up far more airborne carbon dioxide (CO2) than previously realised, although the marine ecosystem may suffer damage if this happens, a new study into global warming says.

The sea has soaked up nearly half of the CO2 that has been emitted by fossil fuels since the start of the Industrial Revolution.

But a key role is played by plant micro-organisms called phytoplankton, which take in the dissolved gas at the ocean's sunlit surface as part of the process of photosynthesis. This plankton dies and eventually sinks to the ocean floor, thus storing the carbon for potentially millions of years.

One of the big questions is how much more of CO2 the sea can absorb.

If, like a saturated sponge, the oceans cannot take up any more, atmospheric concentrations of CO2, the principal greenhouse gas, would sharply rise and stoke global warming.

Another concern is that rising levels of dissolved CO2 also causes acidification of seawater. Wildlife such as coral, which secretes a skeletal structure, are known to be affected by acidification but the impact on other marine species is largely unknown.

In an innovative experiment reported on Sunday in Nature, researchers closed off part of Raune fjord in southern Norway to see how plankton reacted to different levels of CO2

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