Ecosystem Spotlight: Antarctic Seas

Desolate Antarctica is the most uninhabited continent on Earth. Its barren ice fields are home to no large land animals and no plants. Those creatures that do inhabit the Antarctic continent, such as penguins and seals, depend on the ocean for sustenance, and it is in the ocean that the majority of Antarctic life is to be found. Unlike the Arctic, Antarctica is a solid landmass surrounded by ocean, albeit one divided into many large sub-continents. These are joined by huge ice sheets, underneath which dwells an ecosystem unlike anything else in the world.
The near-freezing temperatures of Antarctica's waters have forced many animals to evolve special strategies to cope with the cold. Whales and seals all have a thick layer of fat under their skin called blubber, while penguins have densely packed feathers that trap air and serve as a sort of "bubble-wrap" to keep out the cold (polar bears and sea otters, which live in the Arctic, have fur that does the same thing).
Creatures that stay in the cold ocean their whole lives have even more unique ways of surviving the cold. Many fish that live in Antarctica produce a naturally occurring antifreeze chemical in their blood to prevent it from freezing. These fish all belong to a single group, the icefishes, or Notothenioidei, which have come to be the dominant fish in the seas of Antarctica. However, they are by no means the only animals living there.
The clear, oxygen-rich water of the Antarctic ocean encourages invertebrates to grow to gigantic sizes. Giant starfish, over a foot across, swarm around holes in the ice, scavenging on scraps left by penguins and seals, and searching for dead fish and crustaceans. Isopods the size of mice--distant relatives of the familiar garden pillbug-- crawl along the seabed, eating whatever detritus they can find. These creatures are preyed on by other invertebrates, such as octopuses, which in turn are eaten by fish and by seals and whales. Even the smaller invertebrates are remarkable, including the only species of sea anemone to grow on icebergs.
The very largest of Antarctica's giant invertebrates--and the largest invertebrate on the planet-- is the colossal squid, which can grow up to forty feet in length and weigh in at half a ton. Never seen alive until 2007, the colossal squid has the largest eyes of any animal, measuring 11 inches across. Its tentacles are tipped with sharp hooks instead of suckers, which it uses to seize prey.
While a great deal of ink has justifiably been spilled over the melting of Antarctica's icecap, less attention has been paid to the threat faced by its marine ecosystem. As the planet is warmed, this ecosystem, adapted as it is to life in subzero temperatures, will be in grave danger.




Unique sea creatures like this jellyfish inhabit the cold ocean surrounding Antarctica. But as the icecaps melt and the oceans are warmed, how safe is their home?