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

Nitrosopumilus maritimus and closely related microbes make up about 30% of marine microbial plankton.

From Science Daily • Mar. 11, 2026

When climate models leave out calcifying plankton, they may miss key steps in the global carbon cycle.

From Science Daily • Feb. 8, 2026

Calcifying plankton, microscopic organisms that form hard shells, help regulate the planet's temperature by capturing carbon and moving it through the ocean.

From Science Daily • Feb. 8, 2026

As plankton grow and die, they help move carbon from the atmosphere into deeper layers of the ocean.

From Science Daily • Feb. 8, 2026

No larger than grains of dust, these transparent larvae swim about in the surface waters, feeding on the microscopic plant life of the plankton.

From "Silent Spring" by Rachel Carson