- STOCKHOLM -- The increasing
acidity of the world's oceans could banish all coral by 2065, a leading
marine expert has warned.
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- Professor Katherine Richardson said sea organisms that
produced calcareous structures would struggle to function in the coming
decades as pH levels fell
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- The expert, based in Denmark, told the EuroScience Open
Forum 2004 that human-produced carbon dioxide was radically changing the
marine environment.
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- CO2 levels are now said to be at their highest level
for 55 million years.
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- Most of it will eventually be absorbed by seawater, where
it will react to form carbonic acid.
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- The normal acidity of the ocean is around pH 8, but experts
predict this could drop to pH 7.4.
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- Scientists fear this increasing acidification could have
a particularly detrimental effect on corals and other marine organisms,
because it reduces the availability of carbonate ions in the water for
them to make their hard parts.
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- Record readings
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- As climate change research has primarily concentrated
on the impacts on land and in the atmosphere, our knowledge of what the
rise will mean is uncertain.
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- However, as there are 78,000,000 gigatonnes of carbon
locked up in ocean sediments compared with 750 gigatonnes of carbon in
the atmosphere, the rise could have very serious implications for the carbon
cycle, Professor Richardson believes.
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- "It makes sense that the component of the Earth's
system we need to understand the most is the biggest," said the researcher
from the Department of Marine Ecology in Aarhus, Denmark. "But it
just happens to be the one that's most difficult for us humans to explore."
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- CO2 levels in the atmosphere, driven up by the burning
of fossil fuels, currently stand at about 380 parts per million (ppm) -
up from their pre-industrial mark of around 280 ppm.
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- Carbon dioxide is removed from the atmosphere by microscopic
ocean-dwelling plants called phytoplankton, through photosynthesis. But
one group, called the coccolithophorids, also produce calcium carbonate
platelets, called liths.
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- Each lith is only about 2.5 micrometres (millionths of
a metre) across but a very great many are produced each year.
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- It is estimated that blooms of the dominant species,
Emiliania Huxleyi , annually cover about 1.4 million sq km of the ocean.
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- When they die, they rain down to the ocean floor, in
the process locking carbon away in a vast sediment store. This biological
pump helps to control the exchange of carbon between the oceans and atmosphere.
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- Knowledge search
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- " E. Huxleyi has dominated the world's oceans since
the Holocene, but prior to that a different species was responsible for
moving all the carbon to the bottom," explained Professor Richardson.
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- "It's anyone's guess if another species would step
in if E. Huxleyi can't tolerate the more acidic conditions."
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- Scientists are beginning to address the gaping holes
in our knowledge. Last week, the UK's academy of science, the Royal Society,
announced a study concentrating on the impact of increased acidity on marine
life.
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- An extra reason for the concern is that scientists have
considered exploiting ocean processes to help mitigate rising CO2 levels.
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- The idea is that by artificially "fertilising"
phytoplankton at the ocean surface, it might be possible to stimulate the
take-up of CO2 - locking away some of the extra CO2 in the atmosphere that
is believed to be forcing global temperatures to rise.
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- If increased acidity begins to hinder the natural removal
of CO2 from the atmosphere, however, then we may lose one opportunity to
reverse any damage induced by human activity.
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- © BBC MMIV http://news.bbc.co.uk/2/hi/science/nature/3605908.stm
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