Antarctic sea creatures hypersensitive to warming
Sun Jan 25, 2009 8:32pm EST
By Alister Doyle, Environment Correspondent
ROTHERA BASE, Antarctica (Reuters) - Thriving only in near-freezing waters,
creatures such as Antarctic sea spiders, limpets or sea urchins may be among
the most vulnerable on the planet to global warming, as the Southern Ocean
heats up.
Isolated for millions of years by the chill currents, exotic animals on the
seabed around Antarctica -- including giant marine woodlice and sea lemons,
a sort of bright yellow slug -- are among the least studied in the world.
Now scientists on the Antarctic Peninsula are finding worrying signs that
they can only tolerate a very narrow temperature band -- and the waters have
already warmed by about 1 Celsius (1.6 Fahrenheit) in the past 50 years.
"Because this is one of the most rapidly warming areas on the planet and
because the animals are so temperature sensitive...this marine ecosystem is
at higher risk than almost anywhere else on the planet," said Simon Morley,
a marine biologist at the British Antarctic Survey at Rothera.
"A temperature rise of only 2-3 degrees (Celsius) above current temperatures
could cause these animals to lose vital functions," he said.
In warmer waters, laboratory studies show that clams and limpets lose the
ability to right themselves if they land upside down. Such a skill is vital
in Antarctica's shallows, where icebergs regularly scrape across rocks on
the seabed.
"Will they be here in 100 years' time?" Morley said, standing by blue tanks
of sea cucumbers, worms and others. "I think that we will see changes in the
ecosystems, more in some species and less in other species.
"It does look as if these mechanisms are truly applicable worldwide," he
said.
Studies of clams in Singapore also show that they find it hard to burrow if
temperatures rise, he said. Coral reefs can also suffer damage if
temperatures rise even slightly.
The U.N. Climate Panel has a best estimate that air temperatures may rise by
between 1.8 and 4.0 Celsius this century, due to a build-up of greenhouse
gases.
Rothera's waters range from about minus 2 Celsius in winter, kept from
freezing by saltiness, to 1 Celsius in summer.
DIVERS, ICEBERGS, INVADERS
On a recent trip into Rothera's bay, Ali Massey and Terri Souster, dressed
in thick black dive-suits, disappeared into the water from a red inflatable
speedboat and re-emerged 20 minutes later with a haul of the
little-understood creatures.
"It is a fascinating place to dive," said Souster, a 24-year-old South
African.
The inshore habitat is largely separate from the open ocean, where penguins
and whales feed on krill that in turn consume algae. Big predators in the
shallows are starfish and fish such as Antarctic cod.
In Antarctica, another linked threat is from icebergs that now scour each
part of the shallow seabed on average once a year -- smashing many of the
creatures.
Divers off Rothera are extending a 5-year study of iceberg scours by placing
small white concrete blocks on the seabed. They are later retrieved to see
how many are cracked by icebergs.
And iceberg poundings could become more frequent since warming could bring a
decline in sea ice. Winter sea ice locks icebergs into position -- when it
melts they can get moved around by winds and tides and swept into the
shallows.
Another worry is that non-native species will arrive off Antarctica if the
oceans warm, perhaps organisms floating on a piece of plastic or stuck on
the hull of a ship. Invasive species, usually transported by humans, can
oust local species.
"It's something we are really concerned about," Morley said, noting that at
current rates of warming the danger was about 50 years away.
(Editing by Louise Ireland)
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