Competing phytoplankton undermines allelopathy of a bloom-forming dinoflagellate

Emily K. Prince, Tracey L. Myers, Jerome Naar, Julia Kubanek

Research output: Contribution to journalArticlepeer-review

43 Scopus citations


Biotic interactions in the plankton can be both complex and dynamic. Competition among phytoplankton is often chemically mediated, but no studies have considered whether allelopathic compounds are modified by biotic interactions. Here, we show that compounds exuded during Karenia brevis blooms were allelopathic to the cosmopolitan diatom Skeletonema costatum, but that bloom allelopathy varied dramatically among collections and years. We investigated several possible causes of this variability and found that neither bloom density nor concentrations of water-borne brevetoxins correlated with allelopathic potency. However, when we directly tested whether the presence of competing phytoplankton influenced bloom allelopathy, we found that S. costatum reduced the growth-inhibiting effects of bloom exudates, suggesting that S. costatum has a mechanism for undermining K. brevis allelopathy. Additional laboratory experiments indicated that inducible changes to K. brevis allelopathy were restricted to two diatoms among five sensitive phytoplankton species, whereas five other species were constitutively resistant to K. brevis allelopathy. Our results suggest that competitors differ in their responses to phytoplankton allelopathy, with S. costatum exhibiting a previously undescribed method of resistance that may influence community structure and alter bloom dynamics.

Original languageEnglish (US)
Pages (from-to)2733-2741
Number of pages9
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1652
StatePublished - Dec 7 2008
Externally publishedYes


  • Chemical ecology
  • Competition
  • Harmful algal bloom
  • Plankton
  • Variability

ASJC Scopus subject areas

  • General Immunology and Microbiology
  • General Biochemistry, Genetics and Molecular Biology
  • General Environmental Science
  • General Agricultural and Biological Sciences


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