Phytoplankton blooms: A 'loophole' in microzooplankton grazing impact?

X. Irigoien*, K. J. Flynn, R. P. Harris

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

347 Scopus citations


Phytoplankton size and relations between phytoplankton and microzooplankton (ciliates and heterotrophic dinoflagellates) biomass are analysed in 12 globally distributed areas. In view of the results, a hypothesis is posed where blooming species are those able to escape control by microzooplankton through a combination of predation avoidance mechanisms (e.g. larger size, colonies, spines, and toxic compounds) at the beginning of the bloom. Factors that help to enhance subsequent bloom development include positive feedback from the poor nutritional status of the phototrophic prey which adversely affects predation, inter-microzooplankton grazing and top-down grazing by mesozooplankton on microzooplankton. Blooming conditions are interpreted as physical or chemical perturbations disrupting the predator-prey controls that normally operate at the level of the microbial loop, opening 'loopholes' into which some phytoplankton species populations can explode.

Original languageEnglish (US)
Pages (from-to)313-321
Number of pages9
JournalJournal of Plankton Research
Issue number4
StatePublished - Apr 2005

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology


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