Heterotrophic picoplankton is the fraction of plankton composed by cells between 0.2 and 2 μm that do not perform photosynthesis.
Cells can be either :
Archaea form a major part of the picoplankton in the Antarctic and are abundant in other regions of the ocean.[1] Archaea have also been found in freshwater picoplankton, but do not appear to be so abundant in these environments.[2]