Orcas are toothed whales that roam widely and are common in Antartica. They hunt large, single prey-fish, squid, penguins, eels and smaller whales. Sperm whales, the other toothed whales in Antarctic waters, dive to extremely deep water to feed on squid and fish.
Phytoplankton: A few species of microscopic single-celled plant-like organisms form large dense populations of cells in the ocean when sunlight returns in the spring. These diatoms and algae are the main producers of the Antarctic ocean ecosystem, and all the animal life depends on them.
Amphipods in the plankton are often sometimes free-swimming, large, red species that, and often are prey of penguins and fish. Other amphipod species live inside jellyfish, ctenophores, and salps, eating their hosts’ food or tissues.
Petrels and other Antarctic seabirds are important predators of krill, copepods, and fish. Some of these birds—the albatrosses and terns—undertake extremely long distance flights, migrating or in search of food. Many seabirds are caught and killed unintentionally by long-line fishing gear.
Jellyfish live in all the world’s oceans, from the surfact to deep water, and many jellyfish in cold polar seas are large. All are predators; they use stinging cells to catch and eat smaller planktonic animals including copepods, krill, and larval fish.
Pteropods are planktonic snails. A 2-millimeter, transparent species is very common, and a 2.5-centimeter brown species is less common. Fish and many other invertebrates eat them.
Squid range from small up to a 4-foot-long species with hooks on its arms. Squid are found in every ocean, and from the surface to great depths. They eat krill, fish, jellyfish, and other squid, and in turn are eaten by seals and whales, and sometimes penguins and albatross.
Weddell Seals and Fur Seals are part of the Antarctic Ocean ecosystem, and krill are major parts of their diets. They, along with all seals, were hunted almost to extinction but are now protected. Southern elephant seals are also a part of this ecosystem.
Crabeater Seals feed on krill and fish, straining them from the water with their teeth. They are a fequent prey of Leopard seals.
Ctenophores, gelatinous planktonic animals found in all oceans, can be as large as 30-centimeters-long in the Antarctic. They are transparent and soft, but also are predatory, catching crustaceans and small fish with sticky secretions. Ctenophores can be found from deep water to just under the ice, where they eat krill.
Fish live from midwater depths to right under the ice, and eat a variety of food from small plankton to crustaceans like krill and amphipods. Many Antarctic fish have anti-freeze compounds in their blood. Fish are consumed by most of the predators.
Salps are transparent, jelly-like, barrel-shaped, 2-inch-long animals that can be single or in long chains, and can build up large populations. They filter phytoplankton out of the water, but it is not clear how many Antarctic ocean predators can—or do—eat sales.
Krill Antarctic krill are crustaceans that form huge swarms in the open water in summer, and are the main food source for Antarctica’s large animals, including penguins, whales, fish, some seals and seabirds, and larger zooplankton. Krill eat a variety of food items, but mostly eat phytoplankton cells, either by catching them in open water, or scraping algae off the underside of sea ice as juveniles.
Copepods are the most common zooplankton in the world’s oceans—tiny, abundant planktonic crustaceans that eat small particles, including phytoplankton, small zooplankton, and detritus. They are eaten by krill and other invertebrates, fish and baleen whales.
Penguins consume krill as the dominant part of their diets, but they also eat other animals, such as midwater fish and amphipods. Several species of penguins breed in Antarctic, but they spend most of the year at sea. Adélie penguins are the most common species around Palmer Station.
Leopard Seals are solitary hunters and fierce predators on penguins and other seals—they are the only seals that hunt other warm-blooded mammals, though they will also eat other things, including krill, fish, and birds. When they catch penguins, they often shake the carcass violently, breaking it apart.
Six species of Baleen Whales are found in Antarctic waters, but their numbers were severely reduced by whaling, and their recovery depends on krill populations. These blue, fin, humpback, minke, southern right and sei whales feed by straining vast amounts of krill from water, though the diets of some species may contain copepods and other small prey.
Antarctic animals all make their living in the ocean, because the land is too cold, dry, and dark for plants and animals. Antarctica's coastal seas are especially important because they shelter an abundant ecosystem, supporting large predators such as penguins, seals and whales. Find out about this unusual ecosystem, and how so many big sea creatures depend on tiny plant cells to keep the system working!
Juvenile Krill aggregate under pack ice in winter, eating microscopic plankton and ice algae that grow in and one the ice.