Characteristics of the Antarctic Ecosystem (Cambridge (CIE) IGCSE Geography): Revision Note

Location of the Antarctic

• Antarctica is located at the South Pole from 66.5° to 90° south of the Equator

• Antarctica is a vast and remote continent surrounded by the Southern Ocean within the Antarctic Circle

• It is considered the world's last wilderness, as it is mostly untouched by human activity because of its harsh climate and extreme environmental conditions

Location of Antarctica and key facts

Characteristics of the Antarctic climate

• Colder than the Arctic with average summer temperatures of -28 °C

  • Coastal regions are warmer than inland with a mean annual temperature of -10 °C

  • Interior mean annual temperature is -43.5 °C

  • Average seasonal temperature range is 8 °C to -60 °C

• The continent is a polar desert, receiving precipitation in the form of snow

• Annual mean precipitation is approximately 166 mm

  • The interior mean precipitation rate is 50 mm

  • Whereas it is, on average, 200 mm at the coast

  • Humidity is usually low at 0.03%

  • During winter, more ice forms and the continent can double in size

• The weather is variable and changes suddenly due to the strong katabatic winds from the interior

  • These winds blow snow around and can make visibility very poor

Causes of the Antarctic climate

• The Earth is a sphere with a permanent tilt of 23.5° towards the sun

• Antarctica is at the furthest point from the Equator

• The tilt results in distinct seasons as the Earth orbits the sun

  • 24 hours of daylight as it faces the sun in the summer

  • 24 hours of darkness as it faces away from the sun in winter

• Different areas of the Earth get different amounts of energy from the sun, known as insolation

• Therefore, the equator gains solar energy, but the poles have a deficit of solar energy

  • This means that the sun's energy is less and has to warm a much larger area of land

  • This results in colder temperatures as you move north and south of the equator

  • As the air is cold, it sinks and creates high-pressure areas over both the poles

• The permanent high pressure over Antarctica means that dry, cold air sinks over the interior and limits cloud formation and precipitation

• At the surface, the cold, dry air flows outwards towards the low-pressure areas at the Antarctic Circle, creating the strong, unpredictable katabatic winds

The permanent high pressure over the continent brings cold, dry air and little precipitation

The Antarctic ecosystem

• Antarctica has both marine and terrestrial ecosystems

• The abiotic features of the Antarctic affect the type and number of biotic (flora and fauna) organisms that can survive on the continent

Key abiotic factors of the Antarctic ecosystem

• Temperature

  • Antarctica's extreme cold limits the types of organisms that can survive and impacts biological processes

• Water availability

  • Although there is plenty of ice and snow, liquid water is scarce in arid valleys and ice-free areas

• Wind

  • Antarctica's strong winds cause significant erosion and impact the distribution of organisms

• Light

  • Antarctica's long periods of darkness limit photosynthesis

• Ultraviolet radiation

  • Because the ozone layer is thinner over Antarctica, more UV radiation reaches the surface and harms organisms

• Soil

  • Antarctic soils are cold, dry, and nutrient-poor, which limits the growth of plants and other organisms 

• Marine environment

  • Antarctica's marine ecosystem is rich in nutrients that are brought to the surface by ocean currents and support a complex food web

Key biotic factors of the Antarctic ecosystem

• Plant life

  • The harsh cold temperatures, the frozen soil, and the scarcity of water in Antarctica limit plant growth

  • Antarctica's flora consists of algae, lichens, mosses, fungi, Antarctic hairgrass, and pearlwort

  • These plants can photosynthesize in extremely low temperatures and have adapted in various ways

    • Most plants become dormant to survive the cold, dark winters

    • Plants are small and round-shaped to provide protection from the wind

    • Plants flower and produce seeds during the long summer hours, relying on wind for pollination as there are no insects

    • Fungi, lichens, algae and mosses have simple root systems and absorb water easily

• Animals

  • Antarctica's biotic components are mostly animal-based

  • The Antarctic springtail is the largest dominant terrestrial animal despite being under 3 mm long and living in the soil

    • This tiny soil invertebrate survives by producing antifreeze proteins that keep their body fluids liquid

  • Fauna includes penguins, seals, krill, various fish species, and seabirds, which are not considered terrestrial because they live on both land and sea

  • Animals in the Antarctic have adapted to their ecosystem by developing features such as

    • Layers of fur and insulating blubber (fat)

    • Fat that builds up in the summer acts as an energy source during the long winters when food is limited

  • Birds have waterproof feathers

  • Many birds migrate to warmer areas in winter to find food or reproduce

  • Many animals have physical adaptations, such as

    • Short legs and round, squat bodies

    • Large eyes for seeing prey in the ocean

  • Behaviours such as penguins huddling together to stay warm and save energy

^{Martin Wettstein on Unsplash}

• Marine ecosystems

  • The Antarctic marine ecosystem is rich in life, including phytoplankton, zooplankton, and a wide variety of fish, krill, and marine mammals

  • It supports the largest animal on Earth, the Antarctic blue whale

    • This mammal can grow up to 29 metres long and weigh as much as 199 tonnes

    • The blue whale is a filter feeder, depending on microorganisms such as krill for its nutrition

    • The whale can eat up to four tonnes of krill every day, showing how nutrient rich the waters of the Antarctic are

^{Torsten Dederichs on Unsplash}

Interrelationships in the Antarctic ecosystem

• Although Antarctica may look empty, it is home to ecosystems full of connections between the biotic and abiotic

• Antarctica's food web is not as complex as in other parts of the world

  • Phytoplankton in the sea are the most important producers and form the basis of the food chain

  • Krill sit at the bottom, with just a few top predators—like whales, seals, and penguins—sitting at the top

  • However, krill plays a huge role in keeping the whole ecosystem going and is known as a keystone species

  • Although it is a simple web, it is tightly connected; any changes to one species can quickly affect the remaining species

    • Phytoplankton > krill > fish > penguins

    • If phytoplankton stop photosynthesising, then krill cannot feed, which means fish have no food and penguins starve

• Decomposers such as bacteria, fungi, and small worms break down dead organisms, releasing nutrients that other organisms can reuse

• Fungi and algae live together in lichens, where the fungus protects the algae from drying out, and the algae makes food using sunlight

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Antarctic food web showing interrelationships of energy between prey and predator