CHANGING CURRENTS

The ocean's plants and animals depend on one another. Microscopic animals eat tiny plants, bigger animals eat the smaller animals, and so on. Changes in ocean currents and chemistry could unravel this delicate web and affect everything from plants to gargantuan whales—and people.

Krill usually thrive when coastal winds stir up cooler waters full of nutrients. But when the ocean warms, as it did unexpectedly a few years ago, birds found fewer krill and fish to eat and couldn't feed their young.

Recent changes in ocean currents have also put Magellanic penguins on a diet. When these birds aren't mating, nesting or growing new feathers, they're at sea. They fly under water, diving deep to catch their favorite fatty fishes. But fish move when ocean temperatures rise or fall. Climate changes can mean hungry penguins need to swim farther and settle for any food they can find.