Antarctic marine ecosystem
The Antarctic ecosystem is unique in that the food chains are very short and often based on the availability of krill, which is vital for all animal life forms living in Antarctica.
The waters around Antarctica are high in nutrients and are influenced by physical factors such as temperature, ocean currents, weather and ice.
The connection between organisms within ecosystems can be described based on whether they are producers or consumers of energy.
The food web in the Ross Sea
This diagram shows how the food web in the Ross Sea works. The arrows go from prey species (these get eaten) to predators (the hunters).
Who are the producers?
The major producers are phytoplankton, tiny speck-sized plants that float in the currents. They are usually single celled and use photosynthesis to make energy. There are many different types and species of phytoplankton, for example, one type is called the diatoms, of which there are around 100 known species. Phytoplankton can be thought of as the base of a food chain or web.
Who are the consumers?
There are a number of different consumers – below are just some of them.
Zooplankton
Zooplankton are tiny animals that feed off either phytoplankton or other zooplankton. Zooplankton do not really swim, they float with the currents. A common type of zooplankton you might have heard of is krill, which look like mini crayfish but without the big pincers! Krill are a key species – they are most important in this food chain because they are the food source for the larger consumers such as penguins, sea birds, seals and baleen whales. A decline in krill numbers affects these other species.
A catch of krill
A catch of krill in the codend of the midwater trawl onboard the Tangaroa.
Fish
Antarctica is home to around 100 species of fish. Some of them live in the deep water, whereas others make their home just beneath the sea ice. Most of the fish feed on krill or on each other – a small number of fish eat producers. Antarctic fish can look very strange. One exciting thing about some species of Antarctic fish is their ability to avoid freezing by using anti-freeze proteins in their body tissues. As a result of the special environment, these fish tend to grow very slowly and are usually slow breeders. Extensive fishing damages fish stocks and may lead to the collapse of species, which impacts on the entire food chain.
An Antarctic icefish
An Antarctic icefish species (likely Neopagetopsis ionah) in its preferred demersal habitat, observed on 11 February 2008, using the underwater video system.
Squid and octopus
Around 40 different species inhabit the Antarctic waters. Their food sources are fish and krill.
Seals
Seals are marine mammals that spend a great deal of time in the water, but they return to land to breed. The different species eat prey such as fish, penguins, squid and krill.
Whales
Whales are another marine mammal, but unlike the seals, they are exclusively marine. The largest species of whale can be found in Antarctica – the Blue Whale, which is nearing extinction due to over-fishing. Whales eat krill, fish, squid and seals.
Humpback whale
A humpback whale jumping from the water. Humpback whales are highly vocal and highly social animals. They travel in large groups, sometimes of up to 200 individuals.
What are decomposers?
Dead animals and plants sink to the bottom of the ocean. Here, they are either scavenged by other fish or they are broken down by bacteria.
