zooplankton

Zooplankton are tiny animals that live in oceans, lakes, and other bodies of water. Since they're microscopic, you can't see zooplankton when you're paddling around a pond in the summertime.

The smallest organisms in the sea are known as plankton, a term that includes plants, animals, algae, protozoans — all the microscopic beings that exist in water. You can divide plankton into two categories, phytoplankton (or plants) and zooplankton. That zoo offers a clue about the meaning of this word; like zoology, zookeeper, and plain old zoo, zooplankton has something to do with animals, from the Greek zoion, "an animal."

Definitions of zooplankton
  1. noun
    animal constituent of plankton; mainly small crustaceans and fish larvae
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    type of:
    animal, animate being, beast, brute, creature, fauna
    a living organism characterized by voluntary movement
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