Marine Phyla Pages -- Coastal Carolina University 

MARINE PROTISTA

Marine Protista

  Phytoplankton protists

  Zooplankton protists

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Main

The protista is the oldest of the eukaryote kingdoms.  It is a questionable taxonomic group that includes unicellular eukaryotes (both autotrophic and heterotrophic) and algae.  In some classification schemes, this kingdom is broken up into more than one kingdom, and for our purposes we have placed the marine macroalgae in a separate section of their own.  This section, therefore, is devoted to

• Unicellular photosynthetic protists (including most of the best known members of the phytoplankton)
• Unicellular heterotrophic protists (including many well known members of the zooplankton, and often still referred to by their former name, the protozoa)

On the menu bar to the left, we have divided this section into phytoplankton protists and zooplankton protists.  A few words of caution are needed regarding these categories.  Phytoplankton protists, such as diatoms and dinoflagellates, are well known, but not all phytoplankton are protists.  Phytoplankton include all autotrophic drifters in the water column, and as such include members of the eubacteria (cyanobacteria, prochlorophytes, which together may account for up to 70% of the total oceanic primary production worldwide) and marine algaes (such as Chlorophyta), in addition to the protista.  Even within the unicellular protists, many autotrophic species are heterotrophic as well (autoheterotrophs, such as some dinoflagellates), further blurring the line between phytoplankton and zooplankton.  Similarly, many zooplankton protists are well known, such as foraminifera and radiolarians, but zooplankton as a whole include everything from viruses to vertebrates.  Thus, our section on "zooplankton protists" is NOT a comprehensive site for zooplankton, nor does "phytoplankton protists" encompass all phytoplankton. Not only that, but neither photosynthetic nor heterotrophic unicellular protists are strictly planktonic.  Although we generalize them as such, there are many benthic species, such as benthic diatoms, dinoflagellates, forams, ciliates, etc. , and these groups are abundant and extremely important.