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  

/ 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

See Examples For:

plankton

Hot weather increases plankton levels at the water's surface, drawing jellyfish up, experts say.

From BBC ● Aug. 27, 2026

When touched, these cells fire toxic harpoon-like tubes designed to paralyse prey, such as plankton and small fish.

From BBC ● Jul. 28, 2026

In past strong El Niños, scientists have observed decreased plankton — an important food source for marine animals — and an increased probability of harmful algal blooms.

From Los Angeles Times ● Jun. 15, 2026

The trial in Las Virgenes Reservoir near Westlake Village showed that the system prevented most plankton from being sucked in and killed, he said.

From Los Angeles Times ● Jun. 2, 2026

But Nim liked animals that you could see, and have fun with, so when Jack had said he was going sailing for three days to collect plankton, Nim had decided to stay home.

From "Nim’s Island" by Wendy Orr