Marine
Life
In contrast to the sparsely vegetated, barren, and ice-covered continent,
the oceans surrounding Antarctica support a wealth of plant and invertebrate
animal life.
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Nutrient
Riches
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The Southern Ocean's very cold water
allows more oxygen to dissolve in the sea, which is advantageous
for marine life.
This, along with the up- welling of currents
which bring nutrients from the seabed to feed microscopic
algae at the surface, is the key factor of all life in the
Southern Ocean.
In this marine food chain, the microscopic
algae (or plankton) pro- vide food for krill, which in turn
are eaten by fish, whales, seals and birds.
The food web in the Southern Ocean remains
remarkably simple when compared with other oceans.
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The cold waters are about
four times as productive, acre for acre, as the other oceans of the
world. The first link in this immense food chain is the microscopic
algae which drift in the ocean and are eaten by zooplankton, of which
krill is the most prominent, as well as being the principal food supply
for whales. Krill are shrimp-like crustaceans that grow to 7 or 8
centimeters in length, and form enormous schools, which color the
sea red.
Squid and octopus
are also important to the Antarctic ecosystem, providing food for
sperm whales, seals, penguins, sea birds, and fishes (see Wildlife
Section). It has been estimated that about 55 million tons of
squid is consumed annually by the whales of the Southern Hemisphere;
this is about 75 percent of the world's current total fisheries catch.
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Many hoped krill would provide a cheap,
protein-rich food for the world's famine-plagued regions.
However, despite being relatively easy
to catch, krill have proved costly to process and difficult
to market.
Krill must be processed very rapidly
or their tissues begin to break down, turning black and mushy.
Japan and Russia, which now do most of
the krill fishing, have perfected equipment for peeling and
processing krill rapidly.
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Seals are one of the most
fascinating and unique of Antarctic marine mammals. Seals are aquatic
but, unlike whales, must return to the land or pack ice to breed.
The Antarctic supports a much larger seal population than does the
Arctic, due to larger and more productive feeding areas and a lack
of native predators.
With the end of the
long polar winter comes the arrival of millions of sea birds to breed.
Probably 100 million or more birds breed along the coast and offshore
islands of Antarctica. Most of the sea birds belong to the species
Procellariiformes, which include the albatross (largest flying sea
bird, with the wingspan of some species exceeding 4 meters, the fulmers,
prions, petrels, and shearwaters. The remaining regular sea bird species
encompass shore birds, skuas, gulls, terns, and the penguin. Most
sea birds breed in large concentrations, owing to the scarcity of
snow-free ground used for nesting. The chicks develop quickly and
soon fend for themselves until the approach of winter, when most species
migrate north in pack ice or the open sea--some even to Arctic waters--in
which they spend most of their lives.
Many fish of
Antarctica are the only vertebrates that entirely lack red oxygen-carrying
pigment (hemoglobin) in their blood.  This
adaptation to the cold conditions allows a decrease in blood viscosity
and in the amount of energy required to circulate blood. Most research
has concentrated on the two most abundant groups: the Antarctic
cod Nototheniidae and the ice fish Channichthyidae. Initial
interest focused on the evolution of the groups, their ability to
survive in icy waters, their reproduction and growth rates and their
population age structure. Much
current research is concerned with making more accurate estimates
of growth and population size.
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Antarctica's
Flightless Wonders - the Penguins
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The penguins are the best known and most
numerous of all Antarctic birds.
They are stocky, flightless birds with
wings reduced to flippers with which they propel themselves
through the water.
The common Adelies stand 60 to 70 centimeters
high, while the emperor, largest of the penguins, stands up
to 1.2 meters high and weighs up to 41 kilograms (95 pounds).
Penguins nest in large, dense colonies,
some with 180,000 or more birds; the sight, smell, and noise
of any colony are unforgettable.
Most build nests of stone and there they
incubate one or two eggs.
Only the emperors breed in winter on the
ice along the coast, and they remain in Antarctica permanently.
Like most Antarctic sea birds, they have
evolved to gain features that help conserve body heat--waterproof
plumage, a layer of subcutaneous fat, large and compact bodies.
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