Plankton picoplankton

Fig.1 Generalized pelagic food web [ 13]. The old view of a simple food chain vertical line in this figure) with phytoplankton (mainly diatoms) at the base, herbivorous mesozoo-plankton (mainly copepods) at the second trophic level, and planktivorous fish has been extended to a pelagic food web including nanoplankton (<20 pm), picoplankton (<2 pm), and their protozoan feeders lower left). Herbivorous tunicates and jellyfish as primary carnivores also play a role, as do mixotrophic flagellates. The main pathway of energy flow depends on the nutrient scenarios [13]. DOC=dissolved organic carbon, HNF=heterotrophic nanoflageUates. From [13] with permission of Kluwer Academic Press...

Metzler, P., Gilbert, P., Gaeta, S., and Ludlam, J. (2000). Contrasting effects of substrate and grazer manipulations on picoplankton in oceanic and coastal waters off Brazil. Plankton Res. 22(1), 77-90. 

After the first appearance of cyanobacteria, presumably in microbial mats, the arrival of unicellular cyanobacterial plankton must surely have been rapid. In the modern warm tropical and subtropical oceans, cyanobacterial picoplankton are ubiquitous (Capone et al. 1997), supporting complex microbial consortia, and in the Archaean they could have formed the upper 100 m layer of an open ocean biological community, which may have had great diversity (Karl 2002). Archaeal plankton would have been out-competed for occupancy of the topmost levels, but could have occupied a now more productive underlying lower layer, 100-300 m thick, dependent on the redox debris (including dissolved chemical species) from the overlying oxygenic photosynthesizers. The immediate results. 

C.A. Ochs (1997). Effects of UV radiation on grazing by two marine heterotrophic nanoflagellates on autotrophic picoplankton. J. Plankton Res., 19,1517-1536. 

Classification of the plankton as a whole is often made on the basis of size (Fig. 1.9). The ultrananoplankton (or picoplankton) is composed almost entirely of bacteria, the nanoplankton of algae (phytoplankton), and the macro- and megaplankton of animals (zooplankton), mainly invertebrates. 

Fig. 1. 9 Size classification of plankton (the 0.2 to 2 im size range is often termed the picoplankton).

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