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 also help remove carbon dioxide from the atmosphere through photosynthesis, meaning reduced plankton growth may weaken the ocean's role in storing carbon.

From Science Daily • May 28, 2026

According to a new study, the rapid decline of Arctic sea ice has sharply reduced levels of nitrate, a nutrient essential for the growth of plankton that form the foundation of the region's ecosystem.

From Science Daily • May 28, 2026

Researchers warn that nitrate-poor conditions may favor smaller plankton species in the future.

From Science Daily • May 28, 2026

The researchers determined that this plankton species evolved between 3.5 and 11 thousand years after the Chicxulub impact, though the exact timing varied depending on the site studied.

From Science Daily • Mar. 15, 2026

I had nightmares about what Poseidon might turn me into if I were ever on the verge of death— plankton, maybe.

From "The Sea of Monsters" by Rick Riordan