Globally, a high proportion of all seals live in the marine areas around Antarctica. The population of crabeater seals represents about half of the entire global seal population. By way of comparison, six seal species are found south of the Antarctic Convergence: Antarctic fur seal (Arctocephalus gazella), crabeater seal (Lobodon carcinophagus), Weddell seal (Leptonychotes weddelli), leopard seal (Hydrurga leptonyx), southern elephant seal (Mirounga leonina) and the Ross seal (Ommatophoca rossi).
During the summer season, both toothed and baleen whales can be found in the Antarctic marine environment. The toothed whales sperm whale (Physeter macrocephalus) and orca (Orcinus orca) hunt larger prey, such as fish, squid and small mammals. The baleen whales fin whale (Balaenoptera physalis), common minke whale (Balaenoptera acutorostrata) and humpback whale (Megaptera novaeangliae) primarily graze on plankton which they catch by filtering water through their baleens.
All of the approximately 45 species of bird which have been observed south of the convergence are linked to the marine ecosystem.
Only a couple of the species nest on the continent itself (excluding the Antarctic peninsula): emperor penguin (Aptenodytes forsteri), Adélie penguin (Pygoscelis adeliae), Gentoo penguin (Pygoscelis papua), snow petrel (Pagodroma nivea), Antarctic petrel (Thalassoica antarctica) and south polar skua (Catharacta maccormicki).
Penguins account for 85% of the biomass of seabirds in Antarctica, and the Adélie penguins alone account for half of all penguins.
Around 200 species of fish have been recorded south of the Antarctic Convergence, 80-100 of which are demersal fish.
Many of these species, particularly those which live near the coast, are unique to Antarctica. Seventy five percent of the species are members of five families which belong to the order Nototheniidae, but skates (Batoidea), checker eelpout (Zoarchidae) and snailfish (Liparidae) are also present.
The Southern Ocean is also rich in squid (Cephalopoda), which form an important part of the diet of many larger species of mammals and the seabirds.
Approximately 100 species of algae (including those which live in or on the sea ice) make up the majority of the phytoplankton in the seas around the Antarctic continent. Together with the algae, flagellates are an important part of the nutritional basis in the marine ecosystem.
Zooplankton are dominated by crustaceans such as copepods, amphipods and euphasia species, such as krill.
Krill is a key component of the Antarctic marine ecosystem, with the species Euphausia superba, which is the main source of food for many species higher up the ecosystem, being particularly important.
Other important prey are arrow worms (Chaetognatha), Manetar (Scyphozoa, Siphonophorida), comb jellies (Ctenophora), snails and salps (Thaliacea). The benthic fauna primarily comprises sponges (Porifera) and moss animals (Bryozoa).
With the exception of the seabirds which nest along the coast or in the nunatak area, no vertebrates live on the continent.
The Antarctic microfauna largely consists of protozoa (single-celled organisms), nematodes, rotifers and tardigrades (Tardigradia), as well as microarthropods mites, springtails and fleas.