No land-based vertebrate animals inhabit Antarctica. Invertebrates which can tolerate the lower temperatures, exist in the Antarctic Peninsula but are still considered rare. They range from protozoa (single-celled creatures), rotifers, tardigrades and nematodes to arthropods (mainly mites and springtails). The largest invertebrate is the wingless midge (Belgica antarctica), which grows to 12 mm long. Only 67 species of insects have been recorded, and most are less than 2 mm long. Most of them are parasites, like lice which live in the feathers and fur of birds and seals, where they are protected from the harsh climate for much of the time. Collemola (springtails) are the only free-living insects. They feed on algae and fungi, and remain dormant in winter.
Despite the severe climate, many plants thrive in the Antarctic. There are more than 200 species of lichen and over 50 species of bryophytes, such as mosses. A wide of variety of fungi are also survive the harsh Antarctic conditions. Over 700 species of algae are found in the Antarctic, the majority of which are single-celled plants called phytoplankton. Phytoplankton, protozoa (single celled animals) and bacteria are all important food sources within the Antarctic marine environment. In addition, these microscopic organisms play a crucial role in removing carbon dioxide from the atmosphere.
The surrounding ocean, however, abounds in living creatures. Large numbers of whales feed on the rich marine life, especially krill. Six species of seals (including the crabeater, elephant, and leopard) and about 12 species of birds live and breed in the Antarctic. The most prominent inhabitant of the Antarctic is the penguin. A flightless bird, it lives on the pack ice and in the oceans around Antarctica and breeds on the land or ice surfaces along the coast. Most typical are the Adélie and Emperor penguins.
Derived from the Greek words phyto (plant) and plankton (made to wander or drift), phytoplankton are microscopic organisms that live in watery environments, both salty and fresh. Some phytoplankton are bacteria, some are protists, and most are single-celled plants. Among the common kinds are cyanobacteria, silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores.
Phytoplankton are extremely diverse, varying from photosynthesizing bacteria (cyanobacteria), to plant-like diatoms, to armor-plated coccolithophores (drawings not to scale). (Collage adapted from drawings and micrographs by Sally Bensusen, NASA EOS Project Science Office.)
Like land plants, phytoplankton have chlorophyll to capture sunlight, and they use photosynthesis to turn it into chemical energy. They consume carbon dioxide, and release oxygen. All phytoplankton photosynthesize, but some get additional energy by consuming other organisms.
Phytoplankton growth depends on the availability of carbon dioxide, sunlight, and nutrients. Phytoplankton, like land plants, require nutrients such as nitrate, phosphate, silicate, and calcium at various levels depending on the species. Some phytoplankton can fix nitrogen and can grow in areas where nitrate concentrations are low. They also require trace amounts of iron which limits phytoplankton growth in large areas of the ocean because iron concentrations are very low. Other factors influence phytoplankton growth rates, including water temperature and salinity, water depth, wind, and what kinds of predators are grazing on them.
The food chain is based on phytoplankton, a varied group of tiny free floating plants. In spring and early summer their numbers increase rapidly, producing "blooms" like a think pea soup which can cover thousand of square kilometers of the ocean. These blooms provide a food source which is 300-400 times more concentrated than normal for a variety of zooplankton (tiny animals, especially copepods and krill, which in turn provide food for fish, seals, whales and penguins.
Krill, a Norwegian whaling term meaning "small fry", Krill are one of the most important elements in the Antarctic food chain. They feed on microscopic plants (phytoplankton) that float around the Southern Ocean. The krill, in turn, then become the basic food for baleen whales, seals, penguins and many seabirds.
There are two families of krill: the Bentheuphausiidae family, which consists exclusively of a deep-water species called Bentheuphausia amblyops, and the Euphausiidae family, which consists of 89 known krill species, including -- perhaps most commonly -- Euphausia superba, or Antarctic krill. Unlike Bentheuphausiidae krill, the Euphausiidae family is bioluminescent.
This means that Antarctic krill emit a yellow-green light that is thought to either camouflage the krill's shadow or aid the krill in mating or schooling at night. Krill are invertebrates that grow to about two inches in length and live in large schools, or swarms, as dense as 10,000 krill per cubic meter of water.
They live in the surface waters of the Southern Ocean, which extends north from
the Antarctic continent to the polar front -- an area where the cold water of
the Antarctic submerges beneath the warmer waters of the Atlantic, Indian, and
Pacific Oceans. As this deep, cold water rises to the surface of the Southern
Ocean, it brings nutrients from all the world's oceans into the sunlight, making
this area home to what is possibly the earth's largest assemblage of
phytoplankton. It is this massive gathering of phytoplankton that allows for
such tremendous swarms of krill, which harvest the miniscule phytoplankton
particles with a specially developed feeding basket that filters them out of the
water. The krill also find nourishment by scraping ice algae off the underside
of pack ice, particularly in spring. These are successful techniques,
apparently, since the total biomass, or weight, of Antarctic krill -- which is
estimated to be between 100 and 800 million tons -- may be the largest of any
multi-cellular animal on the planet.
Each spring, over 100 million birds breed around the rocky Antarctic coastline and offshore islands. Around 35 species visit the subantarctic Islands. They range from the magnificent wandering albatross, which flies thousands of kilometres to feed, to gulls, skuas, cormorants and terns, which hunt closer inshore. The wandering albatross has the longest - up to 3.5 meters - wingspan of any bird. The name of this magnificent creature is truly deserved as wandering albatross can travel up to 10,000km of a single feeding trip.
In the Antarctic, there are more species of petrels than of any other bird family. Petrels are birds which are characterized by their tube-like nostrils on the upper beak.
Most return to the same sites each year. Some, like the albatross, mate for life. In addition five species of land birds live all year round on South Georgia, Kerguelen and Marion Islands.
Antarctic Ice Fish
There are about 200 different kinds of fish which live in Antarctic waters,90 per cent of the total number of individual fish belong to the well studied group, the Notothenioidea.
Notothenioidea- Trematomus bernacchii
This sub-order is divided into four families: Antarctic cod, plunder fish, Dragonfish and ice fish.
Other bottom-dwelling fish include eel-pouts, sea snails, rat-tailed fish, hagfish, barracuda, lantern fish and skates are also found in these cold waters. Some species of Antarctic Cod can produce a compound similar to 'anti freeze' in their blood which stops their body fluids from freezing, even when temperatures drop below freezing. It lowers their freezing point to about -2°C.
Penguin and Chick
Credit: Mark Terry
Penguins are flightless birds found in the Southern Hemisphere from the Antarctic to the equator. There are 18 species of penguins in the southern water, seven of them live around Antarctica.
The Adelie and emperor breed on the Antarctic shores and are the only two species found in the Ross Sea area.
Chinstraps breed on islands around Antarctica and gentoos are found from the Antarctic islands to the sub-Antarctic.
Another three species (the King, rockhopper and macaroni) live on the sub-Antarctic islands.
Because ice covers almost all of Antarctica, penguins have to get all their food from the sea, where they spend about half their time. They are able to dive very deeply (emperors can dive to 250 meters) and all are excellent swimmers. The feet and tail act as a rudder and the flippers as propellers. They feed mostly on small fish and krill, each one captured individually. The penguins are also food for other ocean predators: leopard seals and killer whales. On land their main predator is the skua, a bird which takes both eggs and chicks.
Southern Elephant Seal
All seals that live in the cold waters near the Antarctic are called 'pinnepeds'. Six types live in Antarctica: Antarctic Fur Seals, Crabeater Seals, Leopard Seals, Ross Seals, and Weddell Seals.
The Southern Elephant Seal is the largest of all the pinnepeds and one of the largest mammals other than whales. Fully grown males may reach a length of 4.5 meters and weigh about 4,000 kilograms. They are of course well adapted to the cold climate, with their big round bodies, layers of blubber and small extremities.
Seals catch most of their prey under water, but spend some time on land or ice floes giving birth, raising their young and basking in the sun.
On land they are quite ungainly but in the water they are very graceful and are excellent swimmers. Much larger numbers of seals are found in the Antarctic compared to the Arctic, which reflects the much greater abundance of food resources in the Southern Ocean.
Many Southern Ocean whales are migratory, heading to tropical waters during the Antarctic winter. They are found there in the summer, feeding on krill and other marine resources. Fourteen species of cetaceans (the name given to whales, dolphins and porpoises) are found in Antarctica. Of these, twelve are whales. There are two groups, the baleen whales and the toothed whales.
Baleen is a huge hairy-edged plate in the whale’s mouth, which acts as a sieve. The whale sieves out krill, small fish and crustaceans.
Six species of baleen whales are found in Antarctica, including the huge blue whale, which is the largest animal that has ever lived. It grows up to 24 meters and can weigh 84 tons. Other baleen species are the fin, southern right whale, sei, minke and humpback. Four species of toothed whales are found in Antarctica. Except for the sperm whale, they are much smaller than the baleen whales and weren’t widely hunted. The other species are the southern bottlenose whale, the orca whale and the southern fourtooth whale. They all have teeth and feed on fish and squid.
Credit: British Antarctic Survey, New Zealand Antarctic Program, Seal Conservation Society, U.K. Royal Navy