http://www.smh.com.au/text/articles/2003/10/08/1065601915788.htm
Picnicking penguins pop up at the polynya
Date: October 9 2003
By Andrew Darby
How do you get to your food when it's locked away under ice? For
Antarctic penguins, opening the fridge door can mean making tracks for
the nearest polynya.
These vital "lakes" in encircling pack ice may stay open as entrances
to the sea even in mid-winter.
American research released yesterday is said to show for the first time
how much penguins depend on nutrients linked to polynyas.
However, Australian work goes a step further. It indicates that a
polynya may act as a doorway to the pack ice zone beyond.
A Stanford University study used satellite data to look at 37 coastal
polynyas around Antarctica. The largest in the Ross Sea measured
396,500 square kilometres, or almost half the size of NSW.
The Stanford team watched seasonal changes in polynyas' size, as well
as in the abundance of microscopic marine plants called phytoplankton
that form the base of the polar food chain.
Polynyas (which take their name from the Russian for "areas of open
water") are said to provide ideal conditions for blooms of
phytoplankton which are eaten by krill; the tiny but abundant krill
are, in turn, a vital food source for most other Antarctic marine life.
The Stanford team found that more than 90 per cent of Adelie penguin
colonies in eastern Antarctica lived near coastal polynyas. The more
productive polynyas supported larger penguin populations, because there
was more krill and shorter distances to travel for food.
However, work led by the Australian Antarctic Division with
satellite-tracked Adelies indicates they see polynyas not as a constant
food source, but as an easy way into the food-rich pack ice zone.
"Adelies make straight for the polynya, and they will start feeding
around the sea ice in its outer boundary," said Dr Knowles Kerry from
the federal Environment Department's Australian Antarctic Division.
"But it's the open water they want, rather than what's in it . . . They
spend their time in the pack ice."
The picture is less clear for emperor penguins which breed in winter, a
time when polynyas could save them days of travel. The division's Dr
Barbara Wienecke said emperors near the French Dumont d'Urville base
headed straight towards polynyas in winter; but others near Mawson did
not seem to use them at all.
"I can absolutely swear the birds know what they are doing," Dr
Wienecke said. "It's just that we don't quite know. Yet."
Birding-Aus is on the Web at
www.shc.melb.catholic.edu.au/home/birding/index.html
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