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

The team determined that 53% of zooplankton and 60% of micronekton, which feed on zooplankton, would be affected by mining waste discharge.

From Science Daily • Nov. 8, 2025

But just as researchers uncover this service to our planet, threats to the zooplankton are growing.

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

What zooplankton lacked in size they made up for in numbers.

From "The Wild Robot Protects" by Peter Brown