Sunday Times (London, UK)  [Printer-friendly version]
February 26, 2006


[Rachel's introduction: As global carbon dioxide levels rise, the
oceans are growing more acidic. Scientists now believe that a
critical threshold for sea-life is being crossed, which could further
the decline of corals and shellfish populations which are highly
sensitive to acidity levels. This in turn would reduce the uptake of
C02 (oceans absorb about half the C02 we produce) worsening the
problem of global warming.]

By Jonathan Leake

The world's coral reefs could disappear within a few decades along
with hundreds of species of plankton and shellfish, according to new
studies into man's impact on the oceans.

Researchers have found that carbon dioxide, the gas already blamed for
causing global warming, is also raising the acid levels in the sea.
The shells of coral and other marine life dissolve in acid. The
process is happening so fast that many such species, including coral,
crabs, oysters and mussels, may become unable to build and repair
their shells and will die out, say the researchers.

"Increased carbon dioxide emissions are making the world's oceans more
acidic and could cause a mass extinction of marine life similar to the
one that occurred on land when the dinosaurs disappeared," said
Professor Ken Caldeira of the Carnegie Institution's global ecology

When CO2 produced by burning fossil fuels dissolves in the ocean, it
forms carbonic acid. A little of this can benefit marine life by
providing carbonate ions ' a vital constituent in the biochemical
process by which sea creatures such as corals and molluscs build their

Caldeira found, however, that the huge volumes of carbon dioxide being
released by humans are dissolving into the oceans so fast that sea
creatures can no longer absorb it. Consequently, the levels of
carbonic acid are rising and the oceans are "turning sour".

Speaking at the American Geophysical Union's ocean sciences conference
in Hawaii last week, Caldeira said: "The current rate of carbon
dioxide input is nearly 50 times higher than normal. In less than 100
years, the pH (measure of alkalinity) of the oceans could drop by as
much as half a unit from its natural 8.2 to about 7.7."

This would mark a huge change in ocean chemistry. The shells of marine
creatures are made of calcium carbonate, the same substance as chalk,
which is vulnerable to acidity. Even a slight increase in acidity
would mean many creatures would dissolve. Others might be able to
rebuild their shells but would be unable to reproduce.

Nature, the scientific journal, recently published a study by Jim Orr,
of the Laboratory for Science of the Climate and Environment, Paris.
It said that by 2050 the Southern Ocean and subarctic regions of the
Pacific might be so acidic that the shells of smaller marine creatures
would start eroding.

Such a loss would have disastrous consequences for larger marine
animals such as salmon, mackerel, herring, cod and baleen whales.
These all feed on pteropods, or sea butterflies, one of the species
most threatened by rising acidity.

Last week another warning was issued about the threat of acidity to
sea life at the annual meeting in St Louis of the American Association
for the Advancement of Science.

Katherine Richardson, professor of biological oceanography at Aarhus
University in Denmark, said: "These marine creatures do humanity a
great service by absorbing half the carbon dioxide we create. If we
wipe them out, that process will stop. We are altering the entire
chemistry of the oceans without any idea of the consequences."

Copyright 2006 Times Newspapers Ltd.

[For more information about the issue of ocean acidification see the
March edition of Scientific American article 'The Dangers of Ocean