Jordi Chias / Gentoo penguins (Pygoscelis papua) swimming together and porpoising in search of krill, Antarctic Peninsula, Antarctica.

Jordi Chias / Gentoo penguins (Pygoscelis papua) porpoising, swimming together in search of krill, Antarctic Peninsula, Antarctica.

Inaki Relanzon / Whale Shark (Rhincodon typus), eating krill and plankton at the surface. Gulf of Mexico, Mexico, North America, August.

Richard Herrmann / Blue Whale (Balaenoptera musculus) feeding on krill, Coronado Islands, Baja California, Mexico

Steven Kazlowski / Crabeater seals (Lobodon carcinophagus) and seagulls feeding on a school of krill in waters off the western Antarctic Peninsula, Southern Ocean

Ingo Arndt / Antarctic Krill (Euphausia superba) with yellow algae in stomach, a small shrimp-like crustacean is the most important zooplankton in the Antarctic food web, Weddell Sea, Antarctica

Flip Nicklin / Antarctic Krill (Euphausia superba) feeding on algae-covered ice, a small shrimp-like crustacean is the most important zooplankton in the Antarctic food web, Antarctica

Flip Nicklin / Antarctic Krill (Euphausia superba) mass feeding on algae growing on underside of ice, Antarctica

Flip Nicklin / Antarctic Krill (Euphausia superba) a small shrimp-like crustacean is the most important zooplankton in the Antarctic food web, Antarctica

Flip Nicklin / Antarctic Krill (Euphausia superba) mass, Antarctica

Flip Nicklin / Antarctic Krill (Euphausia superba) crustacean, Antarctica

Flip Nicklin / Antarctic Krill (Euphausia superba) schooling underwater, this small shrimp-like crustacean is the most important zooplankton in the Antarctic food web, Antarctica