07 August 2009

121 to Go - The "Other" CO2 Problem: Ocean Acidification (Be Afraid, Be Very Afraid)

From a Macleans.ca article by Nancy Macdonald.
Scientists ... say the oceans are facing a terrifying new threat that will affect the entire marine food chain: the water is slowly but surely becoming more acidic.

More than 80 per cent of the heat generated by climate change and a third of all carbon dioxide released into the atmosphere winds up in the ocean. That carbon dioxide - a whopping 118 billion tons - is not innocuous, as scientists once thought. When it dissolves in briny seawater, it produces an acidic molecule known as carbonic acid (the same substance used in soft drinks). Seawater pH is now between eight and 8.3 in most areas, 30 per cent lower than in pre-industrial times....

In 1998, before the issue had hit even the scientific radar, oceanographer Joanie Kleypas was at a Boston conference with top U.S. biologists. With access to early experimental data, she was doing "back-of-envelope" carbon calculations relating to ocean pH when, "all of a sudden," she realized the math was spelling a potential marine disaster. She was so shocked by the magnitude of the problem that she ran from the boardroom and threw up in a nearby bathroom. 

The geological record is "terrifying," she says from her Boulder, Colo., office at the National Center for Atmospheric Research. The last time the ocean's pH changed anywhere nearly as rapidly was 55 million years ago in an event oceanographers call the "Palaeocene-Eocene thermal maximum," or PETM, and there was a mass extinction of calcareous organisms. Now "we seem on track to do in about 300 years what PETM did over 3,000 years," says Debby Ianson, a climate modeller with the Department of Fisheries and Oceans [in Canada].

While sea grasses and jellyfish will thrive in a more acidic environment, marine organisms with calcium carbonate shells likely will not. Indeed, shells and mollusks start to dissolve within 48 hours in seawater as acidic as the oceans are projected to be by the end of the century. So does coral - which is already suffering the impacts of global warming, local pollution, overfishing and habitat destruction.

Battered by so many stressors, coral reefs, which are home to 25 per cent of all marine life, will almost certainly disappear, robbing fish of the crevasses and critical refuge from the awaiting "wall of mouths," says Simon Fraser University biologist Nick Dulvy. Some 20 per cent of all coral reefs have already been destroyed, including a full 80 per cent of all Caribbean reefs, while another 50 per cent teeter on the brink....

It's early days yet, but the acidification process is happening 10 times faster than previously believed, according to the latest science....

Ocean acidification is "essentially irreversible" during periods measured in mere decades, according to Britain's Royal Society.... In geologic terms, a quick change occurs over 10,000 years, but the acidification of the oceans appears to be happening over a period of 50 to 100 years.

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