Friday, February 19, 2010

Jellyfish and Antarctica

A Gentoo penguin feeding her young krill
From Telegraph.UK:

The results of the largest ever survey of Antarctic marine life reveal melting sea ice is decimating krill populations, which form an integral part of penguins' diets.

The six-inch-long invertebrates, also eaten by other higher Southern Ocean predators such as whales and seals, are being replaced by smaller crustaceans known as copepods.

These miniscule copepods, measuring just half a millimetre long, are too small for penguins but ideal for jellyfish and other similarly tentacled predators.

Huw Griffiths, a marine biologist, said the shifting food web, coupled with shrinking ice sheet breeding grounds, could seriously affect the world's favourite Antarctic animal.

Mr Griffiths, of British Antarctic Survey (BAS), said: ''Marine animals spent millions of years adapting to the freezing, stable conditions of the Antarctic waters and they are highly sensitive to change.

''The polar oceans are rich in biodiversity. But if species are unable to move or adapt to new conditions they could ultimately die out.

''Copepods are 120 times smaller than krill, which is inevitably going to affect all the things that feed in that area.

''Penguins, sea birds, whales are all used to catching large items of prey. But creatures with tentacles - like jellyfish are going to have more food value out of smaller prey.

''This kind of predator will do better in this warmer environment.

''We already have huge numbers of amazing looking jellyfish. They are not quite invading but numbers will go up to the point where they become the dominant group.

''And if the waters continue to warm there will not only be a shift between species that are already there, but new species will be able to come into the area.''

...Mr Griffith's research is based ON the Census of Antarctic Marine Life (CAML) and he presented his findings at the American Association for the Advancement of Science (AAAS) in San Diego on Thursday.

The census began in 2005 and will provide the benchmark for future studies on how the diverse sea-floor creatures living in Antarctica's waters will respond to predicted climate change.

More than 6,000 different species living on the sea-floor have been identified so far and more than half of these can only be found on the icy continent.

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