A dynamic habitat
Each winter, an area of the Southern Ocean roughly the size of the United
States freezes around the Antarctic coastline.
This sea ice provides a protective layer over the ocean: a cover that
insulates it against the strong winds and cold temperatures above, and
creates a sheltered habitat for life to flourish.
Sea ice ecosystems
Sea ice ecosystems begin with single-celled species, including bacteria,
protozoa and microscopic phytoplankton (sea plants) such as algae. They
grow on the underside of the sea ice, which acts as a substrate – the
equivalent of soil in the lower latitudes.
Miniature ‘forests’ of microscopic organisms create a banquet for tiny
animals – zooplankton such as copepods and Antarctic krill – which graze
on the underside of the ice.
These tiny animals form the basis of the food web, providing nutrients and
energy to seals, penguins, whales and other marine creatures.
Emperor penguin rookeries
While the underside of the sea ice is an important habitat for Antarctic
algae, krill and other small plants and animals, the sea ice surface is an
important habitat for the largest penguins on the planet: emperor
penguins.
Emperor penguins breed, incubate their eggs and raise their young on the
sea ice. They need a solid, stable platform of sea ice for around 9 months
each year, to allow their chicks to mature and become independent before
the sea ice breaks apart.
Penguin colonies on unstable ground
Emperor penguins are highly sensitive to changes in sea ice.
If sea ice forms too late, or there is too little, emperor penguins do not
have enough space to breed, raise chicks, hide from predators and rest
while molting (replacing their damaged feathers).
If there is too much sea ice, the distance between their colony and their
open water feeding grounds becomes too large. This longer journey can
lead to exhaustion and starvation for emperor penguins and their chicks.
Even when the amount of sea ice is just right, if it breaks up before the
chicks are fledged and independent, entire generations can be lost.
Penguins abandon colony
Since then, sea ice cover has continued to decline.
In the summer of 2022 sea ice in Antarctica’s Bellingshausen Sea plunged
to historic lows. Some areas were completely ice-free for the first time in
the satellite record.
In the spring, emperor penguin colonies in the surrounding area
suffered widespread breeding failure when the sea ice broke up before the
chicks had fledged.
Entire ecosystems at risk
Penguins are an indicator species: the health and size of their population
reflects the overall health of their ecosystem.
Research has shown that some phytoplankton communities are
changing in areas with less sea ice. Salps are becoming more common
and Antarctic krill are shifting poleward in search of cooler waters and
winter sea ice.
Adaptations in the Antarctic sea
Animal adaptation
Emperor penguins Emperor penguins have large
reserves of energy-giving body
fat and a relatively low level of
activity during winter. They are
very social creatures, and one of
their survival mechanisms is to
huddle together to keep warm.
This huddling instinct means that
they do not defend any territory.
The emperor penguin is the only
species of penguin that is not
territorial.
Gentoo penguins Like all penguins, gentoos are
awkward on land. But they’re
pure grace underwater. They
have streamlined bodies and
strong, paddle-shaped flippers
that propel them up to 22 miles
an hour, faster than any other
diving bird
King penguins Their lush feathers protect them
from bitter sub-Antarctic
weather. The plumage has four
layers: the outer layer is oily and
waterproof and encloses three
downy layers for insulation. An
adult king penguin can hold its
breath for 23 minutes and dive
over 1,000 feet deep in search of
food.
Blue whale Like many other marine
mammals such as seals and
dolphins, blue whales have a
layer of thick blubber. This keeps
them warm in freezing
temperatures, which is helpful if
they're swimming around in the
Arctic or Antarctic seas. Blubber
also helps them to stay buoyant,
so they float in water rather
than sink.
Krills Krill have the ability to shrink
their bodies and undergo long
periods of starvation. These
adaptations allow them to
survive during the winter
months in the arctic
Seals in general Seals are well adapted to
cold polar environments
with thick blubber layers
that act both as a food
reserve and insulation.
Most seals also have a
layer of fur, giving
additional insulation on
land.
