phytoplankton
noun
phy·to·plank·ton
ˌfī-tō-ˈplaŋ(k)-tən 
-ˌtän
plural phytoplankton also phytoplanktons
: minute aquatic photosynthetic organisms (such as dinoflagellates, diatoms, and cyanobacteria) : photosynthetic plankton of freshwater or marine environments
Twenty to 40 different species of phytoplankton … can coexist within a single cubic centimeter of water, all vying just for light and a handful of nutrients.—
O. Baker
O. BakerPhytoplankton—myriad small, mostly unicellular algae and bacteria that occupy the surface waters of seas and lakes—dominate aquatic primary production, and over time they have radically altered Earth's atmosphere.—Robert Riding
Robert RidingPhytoplankton form the foundation of marine food chains, and their seasonal blooms are responsible for more than half the photosynthesis, and the resulting production of oxygen, that occurs on Earth.—Robin George Andrews
Robin George AndrewsAntarctic krill are thumb-sized crustaceans that feast on drifting phytoplankton …—Usha Lee McFarling
compare zooplankton
Usha Lee McFarlingExamples of phytoplankton in a Sentence
Recent Examples on the Web
This is important because phytoplankton are the beginning of the food chain in the ocean and help sequester significant amounts of carbon.
—Leah Sarnoff, ABC News, 4 June 2025
Iron is essential for the growth of microscopic phytoplankton in the ocean, but industrial emissions contain aerosolized iron, which quickly dissolves in the ocean and disrupts nutrient balances, the authors noted.
—Sharon Udasin, The Hill, 2 June 2025
On Earth, the gases are only produced by life, primarily microbial life such as marine algae like phytoplankton, according to the researchers.
—Eric Lagatta, USA Today, 2 June 2025
The amount of algae that produce toxins, also known as phytoplankton, is normally small and doesn’t pose a threat.
—Karen Garcia, Los Angeles Times, 10 May 2025
See All Example Sentences for phytoplankton
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Leah Sarnoff, ABC News, 4 June 2025
Iron is essential for the growth of microscopic phytoplankton in the ocean, but industrial emissions contain aerosolized iron, which quickly dissolves in the ocean and disrupts nutrient balances, the authors noted.
—Sharon Udasin, The Hill, 2 June 2025
On Earth, the gases are only produced by life, primarily microbial life such as marine algae like phytoplankton, according to the researchers.
—Eric Lagatta, USA Today, 2 June 2025
The amount of algae that produce toxins, also known as phytoplankton, is normally small and doesn’t pose a threat.
—Karen Garcia, Los Angeles Times, 10 May 2025
See All Example Sentences for phytoplankton
Cite this Entry
“Phytoplankton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/phytoplankton. Accessed 24 Jun. 2025.
Copy CitationKids Definition
phytoplankton
noun
phy·to·plank·ton
ˌfī-tō-ˈplaŋ(k)-tən
-ˌtän
: plankton that is composed of plants
Love words? Need even more definitions?
Merriam-Webster unabridged
Share