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
Phytoplankton—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
Phytoplankton 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
Antarctic krill are thumb-sized crustaceans that feast on drifting phytoplankton …—Usha Lee McFarling
compare zooplankton
Cite this Entry
“Phytoplankton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/phytoplankton. Accessed 7 Jul. 2026.
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