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8.9.3: Prochlorophytes

LEARNING OBJECTIVES

  • Describe the characteristics associated with Prochlorophytes, a member of the Picoplankton

Picoplankton is the fraction of plankton, composed by cells between 0.2 and 2 μm, that is either photosynthetic (photosynthetic picoplankton; ) or heterotrophic (heterotrophic picoplankton). Some species are also mixotrophic. Picoplankton are responsible for the majority of the primary productivity in oligotrophic gyres, and are different from nanoplankton and microplankton. Because they are small, they have a greater surface-to-volume ratio, which enables them to obtain scarce nutrients in these ecosystems.

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Prokaryotes vs. Eukaryotes: Picoplankton observed by epifluorescence microscopy, a technique which allows the detection of certain groups of cells possessing fluorescent pigments; and example would be Synechococcus, which possess phycoerythrin

Prochlorophyta are a photosynthetic prokaryote member of the phytoplankton group Picoplankton. These oligotrophic organisms are abundant in nutrient-poor tropical waters and use a unique photosynthetic pigment, divinyl-chlorophyll, to absorb light and acquire energy. These organisms lack red and blue Phycobilin pigments and have staked thylakoids, both of which make them different from Cyanophyta ( Cyanobacteria ). Prochlorophyta were initially discovered in 1975 near the Great Barrier Reef and off the coast of Mexico. The following year, Ralph A. Lewin, of the Scripps Institution of Oceanography, assigned them as a new algal sub-class.

In addition to Prochlorophyta, other phytoplankton that lack Phycobilin pigments were later found in freshwater lakes in the Netherlands, by Tineke Burger-Wiersma. These organisms were termed Prochlorothrix. In 1986, Prochlorococcus was discovered by Sallie W. Chisholm and his colleagues. These organisms might be responsible for a significant portion of the global primary production.

Prochlorophytes are very small microbes generally between 0.2 and 2 µm (Photosynthetic picoplankton). They morphologically resemble Cyanobacteria, formally known as Blue Green Algae. Members of Prochlorophyta have been found as coccoid (spherical) shapes, like Prochlorococcus, and as filaments, like Prochlorothrix.

Key Points

  • Picoplankton are responsible for the majority of the primary productivity in oligotrophic gyres, and are different from nanoplankton and microplankton.
  • Because they are small, they have a greater surface-to-volume ratio. This enables them to obtain the scarce nutrients in these ecosystems.
  • Prochlorophyta are a photosynthetic prokaryote member of the phytoplankton group Picoplankton. They are abundant in nutrient poor tropical waters and use a unique photosynthetic pigment, divinyl-chlorophyll, to absorb light and acquire energy.

Key Terms

  • prochlorophyta: a photosynthetic prokaryote member of the phytoplankton group Picoplankton
  • picoplankton: plankton composed of cells between 0.2 and 2 micrometers that are either photosynthetic or heterotrophic

 

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