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, Antarctica, works. The arrows represent the energy flow and go from prey species (these get eaten) to predators (the hunters).
Notes: Baleen whales use baleen plates in their mouths to sieve plankton, krill and small fish from the water. Toothed whales have teeth for capturing prey. Krill is the dominant zooplankton species in the Ross Sea.
Skua (flying birds), phalder, 123RF Ltd; Adélie penguin, rhallam/123RF Ltd; Seal, Isselee/123RF Ltd; Fishing trawler, K_Stuart/123RF Ltd; Krill, Uwe Kils, CC BY-SA 3.0; Humpback whale (Baleen whale), Charles J Sharp CC BY-SA 4.0; Sperm whale (Toothed whales), Gabriel Barathieu, CC BY-SA 2.0; Phytoplankton, Public domain; Silverfish, martin_glhf, CC BY-NC 4.0, sourced from iNaturalistNZ; Toothfish, NOAA, Public domain; Zooplankton, Public domain; Flying squid, Darren Stevens, CC BY 3.0; Bacteria, Ivo Sedláček, CC BY 4.0; Benthic invertebrates, NIWA, CC BY-NC-ND 4.0; Ocellated icefish (Fish), Public domain.
Based on an original diagram by M. Pinkerton for NIWA.
Download a PDF version here.
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 form the base of Antarctic food webs.
Antarctic phytoplankton (average size)
Antarctic phytoplankton, Fragilaria kerguelensis (large group), Nitzschia sp. (single small cell on the left) and partial cell of Thalassiosira sp.
Plankton are microscopic organisms that drift in either saltwater or freshwater. Phytoplankton range in size from extremely small – less than 0.001 mm – to substantially bigger (on a phytoplankton scale) – about 0.5 mm in length.
Image: National Institute of Water and Atmospheric Research (NIWA)
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 web 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 and the Southern Ocean are home to over 300 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 antifreeze 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
More than 70 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.
Related content
Discover more about plankton and plankton in the Ross Sea.
In Antarctic life – microalgae, meet a team of researchers investigating the phytoplankton that live on the bottom of the ice and among the sloshy platelet ice layer just below it.
In the Connected article Catch my drift, students learn about phytoplankton – tiny floating organisms that form the base of the marine food web. The article looks at two types of phytoplankton – dinoflagellates and diatoms.
The article Changing times in Antarctica and the related podcast look at some of the possible impacts of a changing sea ice cycle on Antarctic ecosystems and the global climate.
Read about the 8-week voyage by NIWA’s research vessel to survey marine life and habitats around Antarctica in 2008.
Further explore life in Antarctica in:
Activity ideas
In the activity Animal and plant adaptations, students learn about animal and plant adaptations in Antarctic species and use these ideas to design their own unique animal or plant.
The activity Build a marine food web looks at marine food webs in temperate waters, and Making a food web is specific to Antarctica.
The Connected article Who's eating who? explores food webs and adaptations for life.
The teacher resource Antarctica – literacy learning links, lists selected articles from the Connected and School Journal reading series that support the science concepts when teaching about Antarctica.
Browse the wide range of resources under the Antarctica topic.
