Antarctica's land is nearly lifeless, but its seafloor teems with giants
Antarctica has no native land mammals, reptiles or amphibians at all, and its frozen interior is among the emptiest places on Earth. Yet a single square metre of its seabed can hold up to 155,000 animals, and many of the invertebrates there grow far larger than their relatives in warmer seas.
The contrast comes down to water. About 98 percent of the continent lies under ice as much as 4.7 kilometres thick, and some inland areas get only 50 millimetres of precipitation a year, almost all of it snow. The coldest temperature ever measured, minus 89.4 degrees Celsius, was recorded at Vostok Station on the high plateau. The ocean, by contrast, barely changes: its surface stays between about 1 and 1.8 degrees all year. That stability lets seabed communities spread right around the continent, a remarkably wide range for so large a group of species.
Life on land clings to the edges. The western Antarctic Peninsula can receive 900 millimetres of rain and snow a year, and its northern tip is the only mainland spot expected to rise above freezing in summer. The subantarctic islands are milder still. More than 100 million birds nest on rocky shores each spring, among them albatrosses, petrels and skuas, and eight penguin species live on the continent or nearby islands. Hardy mosses and lichens reach even the dry interior, and more than a thousand kinds of fungi have been found.
The Southern Ocean has relatively few fish, just over 320 described species, dominated by snailfish, eelpouts and the notothenioids. Many notothenioids carry antifreeze proteins in their blood, allowing them to swim in water at or slightly below freezing. The largest are two toothfish species that can reach two metres, weigh 100 kilograms and live 45 years.
Human arrivals have brought trouble. Rats, mice, rabbits, cats and livestock have been introduced to some islands, and past hunting and overfishing cut many populations sharply. The Antarctic Treaty System now regulates activity on the continent to protect it for research.
Source: Wildlife of Antarctica
