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

352 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
Externally publishedYes

Bibliographical note

Funding Information:
Thanks are due to all those that contributed to collecting the samples on the different cruises. Special acknowledgement is due to D. Harbour that analysed most of the samples and to R. Davidson who analysed the samples from the Iceland basin. Thanks are also due to J. Huisman, A. Calbet, E. Saiz and J.M. Gasol that commented on previous versions of this article. Ian Joint kindly provided L4 nutrient data. X.I. was supported by a Ramon y Cajal grant and by the project DINAPROFIT (REN2003-09549-C03-03) from the Spanish ministry for science and technology, and by a project funded by the Department of Education of the Basque Country Government (ref EX2002-2). This work was also supported by the NERC, UK through a grant awarded to KJF. The research of RPH is a contribution to the Plymouth Marine Laboratory Core Strategic Research Programme. This study was supported by the UK Natural Environment Research Council through the Atlantic Meridional Transect consortium (NER/O/S/ 2001/00680). This is contribution number 101 of the AMT programme.

ASJC Scopus subject areas

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


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