plankton

noun

plank·​ton ˈplaŋ(k)-tən 

-ˌtän

plural plankton also planktons

: the passively floating or weakly swimming usually minute organisms (such as dinoflagellates, diatoms, copepods, radiolarians, and larval crustaceans and fish) of a body of water

Note: An individual organism found in plankton is technically referred to as a plankter.

… photosynthesizing plankton will grow at their intrinsic rates until nutrients become limiting, light is reduced by shading, and grazing organisms become abundant enough to check the increase …

—W. H. Berger

Almost all marine invertebrates, such as corals, clams, and starfish, reproduce by releasing microscopic larvae that drift in the plankton for a period ranging from minutes to months.

—Randy Olson et al.

Dense schools of menhaden … pour through these waters, toothless mouths … slurping up plankton and detritus …

—H. Bruce Franklin

The prolific zebra mussels have extremely efficient filtering systems, removing enormous quantities of plankton from the water …

—Nelson Bryant

see also phytoplankton, zooplankton

planktonic

plaŋ(k)-ˈtä-nik 

adjective

Other planktonic forms are grazers—tiny animals that filter algae and other organic matter out of the water and consume it.

—Wyoming Wildlife

Examples of plankton in a Sentence

fish that feed mainly on plankton

Recent Examples on the Web

When these upwelling events occur and plankton and algae start appearing in large numbers, other creatures — such as anchovies and sardines — move in to feed, which then brings the sea lions, sea birds and dolphins. —Susanne Rust, Los Angeles Times, 26 Mar. 2025

The filter-feeding species eat plankton by catching the tiny creatures on their mucus and then moving them to their mouth through the help of small hairs, according to the conservancy. —Irene Wright, Miami Herald, 10 Feb. 2025

Covering over 70% of the planet, the ocean is not only home to an astonishing array of biodiversity - from the tiniest plankton to the largest whales. —Vogue, 29 Jan. 2025

Instead of the rapid decline and slow two-year recovery seen on land, plankton in the ocean bounced back within six months and even increased beyond normal levels afterwards. —Victoria Corless, Space.com, 11 Feb. 2025

Word History

Etymology

German, from Greek, neuter of planktos drifting, from plazesthai to wander, drift, middle voice of plazein to drive astray; akin to Latin plangere to strike — more at plaint

First Known Use

1889, in the meaning defined above

Rhymes for plankton

• yankton

Kids Definition

plankton

noun

plank·​ton ˈplaŋ(k)-tən 

-ˌtän

: the floating or weakly swimming animal and plant life of a body of water

planktonic

plaŋ(k)-ˈtän-ik 

adjective