Krill are ecologically very important, because they are near the bottom of the food chain. They make up the largest part of the diet of many animals. In the Southern Ocean, one species, the Antarctic krill, "Euphausia superba", makes up an estimated biomass of over , roughly twice that of the human race. They are eaten by many animals, including whales, seals, penguins, birds, fish, squid, and whale sharks. Of this, over half is eaten by each year, and is replaced by growth and reproduction. 