Tuesday, November 06, 2007

"Mussels face extinction as oceans turn acidic"

Prized as a luxury treat in the best restaurants and a staple food in the human diet for thousands of years, oysters and mussels are now being threatened by rising levels of carbon dioxide.

By 2100 some waters are expected to be corrosive enough to cause the shells of mussels to dissolve

By the end of the century many popular seafood dishes will disappear from our tables as shellfish become increasingly scarce, scientists warn.

They have found that the build up of carbon dioxide in the atmosphere is causing the oceans to grow more acidic as increasing amounts of the gas dissolve in sea water.

This change is reducing the ability of shellfish to make their protective shells. By 2100 some waters are expected to be corrosive enough to cause the shells to dissolve completely, making it impossible for them to survive.

Marine biologists warn that this could have a devastating effect on the ocean environment, as other creatures that eat shellfish will find food increasingly scarce while corals, which make reefs, will also be unable to build their hard external skeletons.

Dr Carol Turley, from Plymouth Marine Laboratory, will tell a conference of doctors at the Royal Society of Medicine that climate change is likely to have a profound effect on human ability to use the oceans as a source of food.

Speaking ahead of the conference later this month, she said the fishing industry would struggle to find supplies of scallops, mussels and oysters for restaurant tables due to ocean acidification...

"The problem this causes has only really emerged very recently.

"Many shellfish use calcium carbonate to make their shells, but the more carbon dioxide in the ocean, the less carbonate is available to those organisms that use it.

"A lot of shellfish are an important food source for fish as well as humans. The impacts of shellfish disappearing could be massive."

Shellfish produce their shells by absorbing calcium carbonate from the water and depositing it around their bodies. Carbon dioxide, however, produces an acid when it is dissolved in water that reduces the availability of calcium carbonate, causing shellfish to grow far more slowly.

Dr Turley explained that in colder seas around the poles, the reaction is more profound and the water may even act to dissolve the shells of shellfish.

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