zooplankton

American  

[zoh-uh-plangk-tuhn] / ˌzoʊ əˈplæŋk tən /

noun

1. the aggregate of animal or animallike organisms in plankton, as protozoans.

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zooplankton British  

/ ˌzəʊəˈplæŋktən /

noun

1. the animal constituent of plankton, which consists mainly of small crustaceans and fish larvae Compare phytoplankton

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zooplankton Scientific  

/ zō′ə-plăngk′tən /

1. Plankton that consists of tiny animals, such as rotifers, copepods, and krill, and of microorganisms once classified as animals, such as dinoflagellates and other protozoans.

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Etymology

Origin of zooplankton

First recorded in 1900–05; zoo- + plankton

Explanation

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."

Example Sentences

"MPs interfere with this process by reducing phytoplankton photosynthesis and impairing zooplankton metabolism," the authors write.

From Science Daily • Jan. 17, 2026

These "unsung heroes" called zooplankton gorge themselves and grow fat in spring before sinking hundreds of metres into the deep ocean in Antarctica where they burn the fat.

From BBC • Jul. 4, 2025

Invasive species such as the overbite clam consumed the zooplankton on which juvenile smelt had fed, toxic chemicals in farm runoff fouled the waters.

From Los Angeles Times • Jan. 14, 2025

North Pacific right whales are baleen whales, which feed by straining huge volumes of ocean water through their comb-like baleen plates that trap copepods and other zooplankton.

From Seattle Times • May 27, 2024

The glowing haze of zooplankton had drifted off.

From "The Wild Robot Protects" by Peter Brown