one important source of food in the antarctic is the krill, which is a general term for the small shrimp-like marine crustaceans. krill are near the bottom of the food chain: they feed on phytoplankton and to a lesser extent zooplankton. krill are a food form suitable for the larger animals for whom krill makes up the largest part of their diet. whales, penguins, seals, and even some of the birds that live in antarctica, all depend on krill.