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About the Phytoplankton
| What are Phytoplankton? | Interesting Facts | Pronunciation |
What are Phytoplankton?
Phytoplankton are a polyphyletic group of unicellular, aquatic, microscopic algae that normally drift with surface currents. They are typically photoautotrophic and can be prokaryotic, eukaryotic, and even mesokaryotic. Phytoplankton are the primary producers of aquatic systems (including freshwater, brackish, & marine), and provide sustenance, directly or indirectly, for nearly all marine life.
Dictionaries and encyclopedias often mistakenly define phytoplankton as plants. Phytoplankton (and all other algae) are not plants. Plants are categorized in the kingdom Plantae, which descended from the algae.
All prokaryotic algae (cyanobacteria) are classified in the kingdom Monera. All eukaryotic algae (even macrophytes) are classified as protists. Monera and protists are phylogenetically more ancient than plants.
The protists once formed the kingdom Protista (aka Protoctista). Protista was ridiculed for containing a myriad of highly unrelated organisms and is therefore no longer regarded a kingdom by modern taxonomy. As a result, eukaryotic algae are now categorized into a few separate kingdoms. One such example is Chromalveolata.
Interesting Facts
- The term 'phytoplankton' was coined in the year 1897.
- Phytoplankton account for less than 1% of Earth's photosynthetic biomass, yet are responsible for more than 45% of Earth's annual net primary production.
- Numerically, the vast majority of oceanic phytoplankton is prokaryotic cyanobacteria.
- Although numerically inferior in abundance, eukaryotic phytoplankters are responsible for the majority of the flux of organics to higher trophic levels and the ocean interior. Aquatic ecosystems are therefore critically dependent on eukaryotic phytoplankton.
- Cyanobacteria are the only extant prokaryotic oxygenic photoautotrophs.
- Macrophytes (which are the seaweeds, not phytoplankton) account for less than 4% of Earth's primary productivity, making them insignificant in terms of production compared to the phytoplankton.
- Oxygenic photosynthesis (to the best of our knowledge) evolved only once in cyanobacteria. Eukaryotes with mitochondria gained the ability to photosynthesize via endosymbiosis of these cyanobacteria over 1.5 billion years ago in the Proterozoic oceans. Gene loss of the engulfed cyanbacterium over time caused it to become a membrane-bound plastid within the eukaryote.
- Some phytoplankton (i.e. Noctiluca scintillans) have lost their chloroplasts and can no longer photosynthesize. They are instead heterotrophic.
Source(s):
Science 16 July 2004: Vol. 305. no. 5682, pp. 354 - 360 DOI: 10.1126/science.1095964
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Pronunciation
Follow these tips to perfect your phycological vocabulary:
- Phytoplankton
Common errors: photoplankton.