One barometer of ocean health is the penguin, whose Southern Hemisphere range extends from the tropical Galapagos Islands near the equator to the ice shelf of Antarctica.
Penguins Barometer for Ocean Health

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Avalanche in the Lemaire Channel. (Ron Naveen/ OCEANITES)

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Pods of killer whales, sometimes 100 strong, patrol the ice edges. Three separate ecotypes live in the Ross Sea, each specializing in a different diet. (John B. Weller)