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Phytoplankton Size in Ecology
  • Size classes of phytoplankton

  • Picoplankton: 0.2-2 µm
    Nanoplankton: 2-20 µm
    Microplankton: 20-200 µm

Phytoplankton size ranges from 0.4 µm to the millimeter scale. Picoplankton (0.2-2.0 µm) was considered only bacteria until the discovery of the unicellular cyanobacteria Synechococcus (ca. 1-1.5 µm; 1979) and Prochlorococcus (0.4 µm; 1989)
  • Surface area-to-Volume Ratio: decreases expo-nentially with cell size; small cells have a high ration, large cells a low ratio
  • Algal growth is dependent on material exchange at the cell surface (CO2, nutrients)
  • Smaller cells with higher SA/V ratio are more efficient in nutrient uptake
  • Algal growth rate increases with SA/V ratio
  • Small phytoplankton dominates in nutrient-poor waters (where total phytoplankton biomass is also low)