Phytoplankton shown highly magnified
Phytoplankton refers to the algal or plant-like component of the
plankton that drifts in the water column. The name comes from the
Greek terms,
phyton or "
plant" and
, meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high numbers, their presence may appear as discoloration of the water.
Phytoplankton, like other plants, obtain energy through a process called
photosynthesis, and so must live in the well-lit surface layer (termed the
euphotic zone) of an ocean, sea, or lake. Through photosynthesis, phytoplankton produce approximately 98% of atmospheric oxygen. Their cumulative energy fixation in carbon compounds (
primary production) is the basis for the vast majority of oceanic (see
chemosynthesis) and some freshwater
food chains. One of the most remarkable and direct food-chains in the ocean is that of phytoplankton fed on by
krill (a type of shrimp), fed on by baleen
whales.
The most important groups of phytoplankton are the
diatoms and
dinoflagellates, but many other groups of algae also occur. One class (
coccolithophores) may also release significant amounts of
dimethyl sulfide (DMS) into the
atmosphere. The DMS is converted to sulfate and these sulfate molecules act as cloud condensation nuclei, increasing cloud cover.
See also
Phytoplankton bloom in the Baltic Sea (July 3, 2001) seen from space]]
External link
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