The opposite to the ice sheet, a lifeless desert, the marine environment is biologically extremely rich. Almost all the life in the Antarctic is concentrated in the sea or on its margins. The biomass is very high owing mainly to the water’s high nutrient and oxygen contents.
Plankton and Krill
The plankton is the basis for any aquatic food chain and is more abundant in polar than in tropical waters. The krill is made up of numerous crustacean species, feeding on plankton, the most frequent of which, Euphausia superba, is like a shrimp. In terms of biomass, krill probably constitutes the Earth’s most abundant element, possibly exceeded 500 million tonnes! In summer, these Crustacea can form swarms covering 500 km². The pink colour is detectable by satellite, not only by fishermen! The very core of the food web, krill provides the staple food for fish, whales, seals, penguins and other birds.
Out of the 20 000 species of fish in the world, less than 300 live in the Southern Ocean. The most characteristic of them, adapted to the polar environment, include the “icefish” (Champsocephalus gunnari, mackerel icefish) whose blood contains no haemoglobin, and Notothenia, a cod icefish which secretes .antifreeze substances.
The flora is scarcely developed on the Antarctic continent. Lichens and mosses are found on rocks, as are microscopic algae in often frozen ice or lakes, also 2 flowering plants in the more temperate Antarctic Peninsula.
However, many species of birds and marine mammals are present on the coast, the sea-ice and in the ocean.
About 40 species of birds, amounting to 200 million individuals, live in the Southern and subantarctic zones; half of them reproducing in summer on the very sparse lands and islands that border the continent. The species most represented are petrels, skuas, terns and of course penguins.
The penguins are birds that are unable to fly but extremely well adapted to the marine environment and to cold. Four species live in the Antarctic, but although chinstrap and gentoo penguins frequent the Peninsula, only the Adélie and Emperor penguins nest on the coastal shores. Penguins form groups, huddling together in thousands on the sea-ice or on the coast forming what are termed rookeries to keep warm. The emperor penguin is the largest and heaviest penguin. It is found in only a few tens of colonies, although each consists of thousands of individuals.
Cetacea (whales, killer whales etc.) and 8 species of Pinnipedia (seals and sea lions), 4 of which reproduce near the continent. However, sea lions do not venture further than the Peninsula and there are no walrus. Several species belong particularly to the Antarctic: the crabeater seals, the most numerous, amount to 15 million individuals, whereas those from Weddell are the most impressive (3 m long and over 400 kg); leopard seals, rarer, feed mainly on penguins: they can swallow up to 20 per day!