Plankton Revealed

Plankton Revealed

Tiny plankton form the base of the ocean food web, which further supports all other aquatic and terrestrial ecosystems across the planet.


9 - 12+


Biology, Earth Science, Oceanography

National Geographic Television and Film

Plankton are an essential component of life on Earth. Marine plankton, found in all ocean ecosystems, play a critical role in maintaining the health and balance of the ocean and its complex food webs. The oxygen, nutrients, and biomass they produce also sustain terrestrial life—from the food we eat to the air we breathe.

Plankton—derived from the Greek root planktos, meaning “wanderer” or “drifter”—are unable to swim against currents, tides, or waves. The word refers to the numerous organisms floating throughout aquatic ecosystems.

Phytoplankton are the tiny, plant-like producers of the plankton community. They include bacteria and algae that form the base of aquatic food webs. Common phytoplankton include diatoms, dinoflagellates, cyanobacteria (blue-green algae), and green algae. Through photosynthesis, phytoplankton use sunlight, nutrients, carbon dioxide, and water to produce oxygen and nutrients for other organisms. With 71% of the Earth covered by the ocean, phytoplankton are responsible for producing up to 50% of the oxygen we breathe. These microscopic organisms also cycle most of the Earth’s carbon dioxide between the ocean and atmosphere.

Zooplankton are the animal-like primary consumers of plankton communities. In turn, zooplankton then become food for larger, secondary consumers such as fish. Zooplankton include microscopic and macroscopic organisms. Some zooplankto—such as copepods, krill, and arrow worms—will drift the ocean as plankton for their entire lives. Other zooplankton live only a portion of their lives as ocean drifters. These include oysters, crabs, and some fish.

Plankton also play a role at the end of the food web—as decomposers and detritivores. These plankton, including bacteria, fungi, and worms, break down and consume dead plant and animal material that falls through the water column as "marine snow." Marine snow often includes fecal matter, sand, soot, skin, and other organic and inorganic particles descending to the seafloor.

Through plankton sampling, scientists like Richard Lampitt can monitor this important component of life on Earth.

Fast Fact

  • Foraminifera (forams) and radiolarians are microscopic zooplankton. The tests, or shells, of these plankton are so abundant that they form the majority of seafloor sediment in many parts of the ocean. The chemicals found in foram tests are also be used by oceanographers to study what the Earth’s climate was like in the past.

Fast Fact

  • Plankton provide the most ancient evidence of life on Earth. Stromatolites are thin layers of fossilized cyanobacteria (a type of plankton) that date from between 2.8 billion to 3.5 billion years ago.

Fast Fact

  • Marine snow got its name because it looks like snowflakes sinking down to the bottom of the ocean. Some marine “snowflakes” can grow to be more than 5 centimeters (1.9 inches) in diameter and can take weeks to reach the seafloor.
Media Credits

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National Geographic Society
Angela M. Cowan, Education Specialist and Curriculum Designer
National Geographic Society
Julie Brown, National Geographic Society
Jeannie Evers, Emdash Editing, Emdash Editing
Production Assistant
Winn Brewer, National Geographic Education
Stock Footage Provider
T3 Media
National Geographic Society
Katy Andres
Julie Brown, National Geographic Society
Alison Michel, National Geographic Society
Last Updated

September 27, 2022

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