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Concept
Picoplancton
Résumé
Picoplankton is the fraction of plankton composed by cells between 0.2 and 2 μm that can be either prokaryotic and eukaryotic phototrophs and heterotrophs:
photosynthetic Photosynthetic picoplankton
heterotrophic Heterotrophic picoplankton
They are prevalent amongst microbial plankton communities of both freshwater and marine ecosystems. They have an important role in making up a significant portion of the total biomass of phytoplankton communities.
In general, plankton can be categorized on the basis of physiological, taxonomic, or dimensional characteristics. Subsequently, a generic classification of a plankton includes:
Bacterioplankton
Phytoplankton
Zooplankton
However, there is a simpler scheme that categorizes plankton based on a logarithmic size scale:
Macroplankton (200–2000 μm)
Micro-plankton (20–200 μm)
Nanoplankton (2–20 μm)
This was even further expanded to include picoplankton (0.2-2 μm) and fem-toplankton (0.02-0.2 μm), as well as net plankton, ultraplankton. Now that picoplankton have been characterized, they have their own further subdivisions such as prokaryotic and eukaryotic phototrophs and heterotrophs that are spread throughout the world in various types of lakes and tropic states.
In order to differentiate between autotrophic picoplankton and heterotrophic picoplankton, the autotrophs could have photosynthetic pigments and the ability to show autofluorescence, which would allow for their enumeration under epifluorescence microscopy. This is how minute eukaryotes first became known.
Overall, picoplankton play an essential role in oligotrophic dimicitc lakes because they are able to produce and then accordingly recycle dissolved organic matter (DOM) in a very efficient manner under circumstance when competition of other phytoplankters is disturbed by factors such as limiting nutrients and predators. Picoplankton are responsible for the most primary productivity in oligotrophic gyres, and are distinguished from nanoplankton and microplankton.
Source officielle
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