30.5.11

Acidificação dos Oceanos - Ocean acidification is latest manifestation of global warming | Environment | The Observer

Os noticiários em Portugal não abrem com problemas ambientais sérios.
Contudo, a acidificação progressiva dos Oceanos deve fazer-nos pensar. Como será a nossa vida se o mar deixar de nos dar peixe ? Que implicações tem um aumento da acidez em 30% num século ?

Ocean acidification is latest manifestation of global warming | Environment | The Observer

Ocean acidification is latest manifestation of global warming

Carbon dioxide pollution adds to threat to world's oceans and marine species

Robin McKie
Robin McKie, science editor
The Observer, Sunday 29 May 2011
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Young teenage woman diver explorin coral reef
By the middle of the century there will probably be only a few pockets of coral left, in the North Sea and the Pacific. Millions of species of marine life will be wiped out. Photograph: Vladimir Levantovsky/Alamy

The infernal origins of Vulcano Island are easy to pinpoint. Step off the hydrofoil from Sicily and the rotten-egg smell of hydrogen sulphide strikes you immediately. Beside the quay, there are piles of yellow sulphurous rocks and chunks of pumice; the beach is made of thick, black volcanic sand; while the huge caldera that dominates the bay emits a constant stream of smoke and steam.

According to legend, this was the lair of the Roman god of fire, Vulcan, who gave his name to the island and subsequently to all other volcanoes. An early eruption here also provided history with one of the first recorded descriptions of a volcano in action.

But Vulcano's importance today has nothing to do with the rock and lava it has spewed out for millennia. It is the volcano's output of invisible carbon dioxide – about 10 tonnes a day – that now interests scientists. They have found that the gas is bubbling through underground vents and is making the island's coastal waters more and more acidic. The consequences for sea life are grim with dozens of species having been eliminated.

That discovery is highly revealing, and worrying, because Vulcano's afflictions are being repeated today on a global scale, in every ocean on the planet – not from volcanic sources but from the industrial plants, power stations, cars and planes that are pumping out growing amounts of carbon dioxide and which are making our seas increasingly acidic. Millions of marine species are now threatened with extinction; fisheries face eradication; while reefs that protect coastal areas are starting to erode.

Ocean acidification is now one of the most worrying threats to the planet, say marine biologists. "Just as Vulcano is pumping carbon dioxide into the waters around it, humanity is pouring more and more carbon dioxide into the atmosphere," Dr Jason Hall-Spencer, a marine biologist at Plymouth University, told a conference on the island last week.

"Some of the billions of tonnes of carbon dioxide we emit each year lingers in the atmosphere and causes it to heat up, driving global warming. But about 30% of that gas is absorbed by the oceans where it turns to carbonic acid. It is beginning to kill off coral reefs and shellfish beds and threaten stocks of fish. Very little can live in water that gets too acidic."

Hence science's renewed interest in Vulcano. Its carbon dioxide springs – which bubble up like burst water mains below the shallow seabed – provide researchers with a natural laboratory for testing the global impact of ocean acidification. "These vents and the carbonic acid they generate tell us a great deal about how carbon dioxide is going to affect the oceans and marine life this century," said Hall-Spencer. "And we should be worried. This problem is a train coming straight at us."

Scientists estimate that oceans absorb around a million tonnes of carbon dioxide every hour and our seas are 30% more acidic than they were last century. This increased acidity plays havoc with levels of calcium carbonate, which forms the shells and skeletons of many sea creatures, and also disrupts reproductive activity.

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