Life Below The Ice
A rich sea life thrives under the barren expanse of McMurdo Sound’s ice pack. For example, frigid waters that would kill many other fish in the world sustain the Antarctic notothenioids, a bony "ice fish" related to walleyes and perch. The notothenioids feature an Antifreeze protein in their bloodstream that prevents them from freezing. Notothenioids account for more than 50 percent of the number of fish species in the Antarctic coastal regions and 90 to 95 percent of the biomass, according to the National Academy of Sciences for the United States.
What some sea creatures lack in numbers, they make up for in their visual presentation. McMurdo Sound divers encounter colorful examples of sea life, including bright yellow cactus sponges and green globe sponges. Starfish, sea urchins, and sea anemones are also present. The latter is noted for its wispy tentacles. Large sea spiders inhabit the deeps of the sound and feed on sea anemone, whereas swarms of Antarctic krill flourish in the upper depths of the icy waters. The shrimp-like krill is a key species in the Southern Ocean food chain for sea life ranging from the baleen whale to penguins. The sound is also home to soft coral, whose flexible form allows the creature to bend so as to feed off the ocean floor, according to the “Underwater Field Guide to Ross Island & McMurdo Sound.”
Antarctic penguins, famous for their waddling walk on surface ice, transform themselves into graceful and powerful swimmers underwater. The Emperor Penguins’ pursuit of squid, fish, and crustaceans leads them to dive as deep as 500 meters. However, the Emperor can go deeper. Scientists have found that the penguin can reach 600 meters for short durations. The much smaller Adelie Penguin is less ambitious. It feeds underwater for up to two minutes at a maximum depth of 170 meters (Underwater Field Guide to Ross Island & McMurdo Sound).
The Weddell Seal out-dives even the Emperor Penguin. The seal can hold its breath for up to 80 minutes and reach a depth of 700 meters (Underwater Field Guide to Ross Island & McMurdo Sound). Scientists diving in McMurdo also encounter the Leopard Seal, and Crabeater Seal. The many-storied Leopard seal is a ferocious predator that preys on warm-blooded animals, such as other seals and penguins, whereas the more sedate crabeater uses its unusual multilobed teeth to sieve krill from the water.
Seals have a natural enemy in the orca or killer whale of McMurdo Sound. The killer whale's voracious appetite leads it to consume up to 500 lb. (227 kg) of food daily. The orcas feature black and white coloring, a large dorsal fin (up to 1.8 m), and enormous strength and size (males can be eight m). The whales travel in pods of up to 30 individuals and can swim up to 46 kilometers/hour or 29 miles/h. (“Underwater Field Guide to Ross Island & McMurdo Sound.”)
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