plankton

American  

[plangk-tuhn] / ˈplæŋk tən /

noun

1. the aggregate of passively floating, drifting, or somewhat motile organisms occurring in a body of water, primarily comprising microscopic algae and protozoa.

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plankton British  

/ plæŋkˈtɒnɪk, ˈplæŋktən /

noun

1. the organisms inhabiting the surface layer of a sea or lake, consisting of small drifting plants and animals, such as diatoms Compare nekton

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plankton Scientific  

/ plăngk′tən /

1. Small organisms that float or drift in great numbers in bodies of salt or fresh water. Plankton is a primary food source for many animals, and consists of bacteria, protozoans, certain algae, cnidarians, tiny crustaceans such as copepods, and many other organisms.

2. Compare benthos nekton

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Other Word Forms

• planktonic
  adjective

Etymology

Origin of plankton

1890–95; < German, special use of neuter of Greek planktós drifting, equivalent to plang-, variant stem of plázesthai to drift, roam, wander + -tos verbid suffix

Explanation

If you set your pet goldfish free in a lake, he might dine on plankton instead of the food you sprinkle in his tank every day. Or, more likely, he might be dinner for a bigger fish. Lakes, seas, and oceans are full of plankton, most of which is so small it can't be seen without a microscope. Anything that floats near the surface is considered to be plankton, whether it's an animal, plant, or something smaller like bacteria, and it's one source of food for fish and whales. The Greek root, planktos, means "wandering or drifting."

Example Sentences

Plankton, which are tiny creatures that float in the sea, have the ability to emit bioluminescence when they are disturbed by a predator or motion.

From BBC • Jun. 25, 2026

Plankton, the abundant tiny creatures that exist in many different types today, were far less diverse during the Miocene.

From Salon • Feb. 17, 2025

Pace — short for Plankton, Aerosol, Cloud, Ocean Ecosystem — is the most advanced mission ever launched to study ocean biology.

From Seattle Times • Feb. 7, 2024

Plankton gobble up carbon dioxide and, as they grow, convert it into organic tissue via photosynthesis.

From Science Daily • Dec. 6, 2023

In the South Pacific, west of Patagonia, there is said to be an immense "sea desert" where there is little Plankton, and therefore little in the way of fishes.

From The Outline of Science, Vol. 1 (of 4) A Plain Story Simply Told by Thomson, J. Arthur