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The Role of Algae in Aquatic Food Webs
  • Concept: The „microbial food web“ complements the classical food chain
  • Pathways: larger phytoplankton (>20 µm) are grazed by herbivorous crustacean zooplankton, which in turn are grazed by planktivorous fish; small phytoplankton is grazed by protozoa (as are bacteria), and protozoa are grazed by „herbivorous“ crustacean zooplankton
  • The Microbial Loop: Dissolved organic carbon (DOC) produced by algae (exudation) and during protozoan and zooplankton grazing is converted into particulate biomass by bacteria and, thereby, re-channelled into the food web. Viruses contribute to DOC production by algal and bacterial lysis
  • Size classes of phytoplankton:
    • Picoplankton: 0.2-2 µm
    • Nanoplankton: 2-20 µm
    • Microplankton:>20 µm
  • Pico- and Nanophytoplankton are part of the microbial food web