Life in the oceans has an impressive variety of animals and plants. Carbohydrates, fats and proteins are absolutely necessary nutrients for all life forms. While animals can not produce these themselves, plants can. Sea animals can not do without Plankton. By eating Plankton or Plankton eaters, they feed themselves with necessary nutrients. Zooplankton, that feeds on Phytoplankton, are food for fish and benthic animals. On their turn, they are on the menu of large (r) fish, marine mammals, seabirds, etc.