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Plankton are microscopic organisms that float freely with oceanic currents and in other bodies of water. Plankton is made up of tiny plants (called phytoplankton) and tiny animals (called zooplankton). The word plankton comes from the Greek word "planktos" which means "drifting."
Phytoplankton: Phytoplankton are primary producers
(also called autotrophs). As the base of the oceanic food web, phytoplankton use chlorophyll to convert energy (from sunlight), inorganic chemicals (like nitrogen), and dissolved carbon dioxide gas into carbohydrates.
Zooplankton: Zooplankton are microscopic animals that eat other plankton.
Some zooplankton are single-celled animals, like foraminifera and radiolarians.
Other zooplankton are tiny crustaceans, like Daphnia. (If you include krill and copepods, which can swim, this group constitutes about 70 percent of all plankton)
Food Web: Plankton is the first link in the marine food chain; it is eaten by many organisms, including mussels, fish, birds, and mammals (for example, baleen whales).
