Antarctic Warming And The Ocean Food

Numbers of krill, a small shrimplike animal at the base of the Antarctic ocean food chain, have fallen by 80 percent since the 1970s, creating food shortages that are endangering larger animals and birds, such as whales, seals, penguins, and albatrosses, especially in the vicinity of the Antarctic Peninsula. Angus Atkinson of the British Antarctic Survey, who led the research, said, "This is the first time that we have understood the full scale of this decline. Krill feed on the algae found under the surface of the sea-ice, which acts as a kind of nursery" (Atkinson et al., 2004, 100-103; Henderson, 2004).

The collapse of ice shelves along some of Antarctica's shores changes the ecology of the nearby ocean, with important effects for wildlife. According to a report by the Environment News Service, the new

Food Chains Antarctica
Krill, at the base of the Antarctic food chain (Jeff Dixon)
Antarctic Food Cycle

Adelie Penguins at a rookery (Jeff Dixon)

icebergs have changed the Antarctic ecosystem blocking sunlight needed for growth of the microscopic plants called phytoplankton that form the underpinning of the entire food web. They are a primary food source for miniscule shrimp-like krill, which in turn are consumed by fish, seals, whales and penguins. Ice shelf B-15 broke into smaller pieces that prevented the usual movement of sea ice out of the region, said Kevin Arrigo, assistant professor of geophysics at Stanford University. Phytoplankton requires open water and sunlight to reproduce, so higher-than-usual amounts of pack ice cause declines in plankton productivity (Breakaway Bergs, 2002).

Populations ofAdelie penguins on the Antarctic Peninsula are falling as their surroundings warm. About 1985, the Biscoe region of the Antarctic Peninsula was home to about 2,800 breeding pairs of Adelie Penguins. By 2000, however, the number had declined to about 1,000. On nearby islands, the number of breeding pairs has dropped from 32,000 to 11,000 in 30 years. "The Adelies are the canaries in the coal mine of climate change in the Antarctic," said ecologist Bill Fraser (Montaigne, 2004, 36, 39, 47). If warming continues, penguins may abandon much of their 900-mile-long home promontory altogether. The archetypal "tuxedoed" species prefer a cold climate even more so than other penguins (Lean, 2002, 9).

Warming has also caused problems for penguins in the Ross Sea. Large icebergs have been blocking the way between their breeding colonies and feeding areas. As a result, the penguins are being forced to walk an extra 30 miles (at a one-mile-per-hour waddle) to get food. Thousands of penguins have died during these treks. Thousands of emperor penguin chicks drowned near Britain's Halley base after ice broke up earlier than usual, before they had learned to swim (Lean, 2002, 9). Penguins cannot fly and so have trouble changing habitat as conditions evolve.

Penguins and whales are only two of the several Antarctic animals that will be threatened in coming years due to rapid habitat change caused at least partially by warming temperatures. Global warming could wipe out thousands of Antarctic animal species in the next 100 years, the British Antarctic Survey said during 2002. An anticipated temperature rise of 2°C, a fraction of what the Intergovernmental Panel on Climate Change (IPCC) forecasts by the end of the twenty-first century, would be enough to threaten large numbers of fragile invertebrates with extinction, said Professor Lloyd Peck from the British Antarctic Survey. These include exotic creatures found nowhere else on Earth, "such as sea spiders the size of dinner plates, isopods—relatives of the woodlouse, and fluorescent sea gooseberries as big as rugby balls" (Von Radowitz, 2002). Peck said, "We are talking about thousands of species, not four or five. It's not a mite on the end of the nose of an elk somewhere" (Von Radowitz, 2002).

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