- Rising carbon dioxide in the atmosphere is threatening
to make oceans too corrosive for marine organisms to grow protective shells,
according to researchers.
-
- If emissions continue unabated, the entire Southern Ocean,
which stretches north from the Antarctic coastline, and subarctic regions
of the Pacific Ocean will soon become so acidic that the shells of marine
creatures will soften and dissolve making them easy targets for predators.
Others will not be able to grow sufficient shells to survive.
-
- The loss of shelled creatures at the lower end of the
food chain could have disastrous consequences for larger marine animals.
North pacific salmon, mackerel, herring, cod and baleen whales all feed
on pteropods or sea butterflies, one of the species under imminent threat.
- "These are extremely important in the food chain
and what happens if they start to disappear is a great unknown," said
Jim Orr, lead scientist on the study at the Laboratory for Science of the
Climate and Environment in Gif-sur-Yvette, near Paris.
-
- Previous studies have suggested it would take centuries
for emissions to acidify the oceans to such an extent, but the latest report,
published today in the journal Nature, claims entire ecosystems will be
threatened much sooner. "Within decades, there may be serious trouble
brewing in these polar oceans," said Dr Orr. "Unlike climate
predictions, the uncertainties here are small."
-
- Carbon dioxide is churned out by the burning of fossil
fuels and other industrial processes. Each day, the average person burns
enough fuel to emit 11kg (about 24lbs) of carbon dioxide, 4kg of which
is absorbed by the oceans. When carbon dioxide is taken up by oceans, it
strips out carbonate ions dissolved in surface waters, so there is less
available for marine organisms to build calcium carbonate shells and exoskeletons
from.
-
- Dr Orr and an international team from Britain, the US,
Japan and Australia combined recent measurements from oceans with computer
models to work out how CO2 levels are likely to change the acidity of oceans
in coming decades if emissions continue as expected.
-
- They found that by 2100, the amount of carbonate available
for marine organisms would drop by 60%. By 2050, there could be too little
carbonate in surface waters for organisms to form shells.
-
- In a follow-up experiment, Victoria Fabry at California
State University San Marcos investigated how marine organisms reacted to
the predicted changes by immersing live pteropods in sea water as acidic
as the models predicted for 2100. She found the shells began to dissolve
rapidly, with pits forming on their surfaces and external layers peeling
away.
-
- Life in the polar oceans will be first to feel the brunt
of rising carbon dioxide levels. Atmospheric carbon dioxide has increased
from pre-industrial levels of around 280 parts per million to 380ppm today.
-
- http://www.guardian.co.uk/climatechange/story/0,12374,1580628,00.html
|
