22 de fevereiro de 2008

Gases de estufa e a saúde do mar

"Every silver lining has its cloud. At the moment, the world's oceans absorb a million tonnes of carbon dioxide an hour. Admittedly that is only a third of the rate at which humanity dumps the stuff into the atmosphere by burning fossil fuels, but it certainly helps to slow down global warming. However, what is a blessing for the atmosphere turns out to be a curse for the oceans. When carbon dioxide dissolves in water it forms carbonic acid. At the moment, seawater is naturally alkaline—but it is becoming less so all the time.

The biological significance of this acidification was a topic of debate at the American Association for the Advancement of Science meeting in Boston. Many species of invertebrate have shells or skeletons made of calcium carbonate. It is these, fossilised, that form rocks such as chalk and limestone. And, as anyone who has studied chemistry at school knows, if you drop chalk into acid it fizzes away to nothing. Many marine biologists therefore worry that some species will soon be unable to make their protective homes. According to Andrew Knoll, of Harvard University, many of the species most at risk are corals."

Ver o desenvolvimento em: Climate change Sour times Economist.com (o bold é meu).

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