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Marine Ecology Progress Series

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MEPS 416:69-78 (2010)  -  DOI:

Allelopathic compounds of a red tide dinoflagellate have species-specific and context-dependent impacts on phytoplankton

Kelsey L. Poulson1,*, R. Drew Sieg1,*, Emily K. Prince1, Julia Kubanek1,2,**

1School of Biology, Georgia Institute of Technology, 310 Ferst Drive, Atlanta, Georgia 30332–0230, USA
2School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, Georgia 30332–0400, USA
*These authors contributed equally to this paper
**Corresponding author. Email:

ABSTRACT: The use of chemical compounds to suppress the growth of competitors is a competitive strategy known as allelopathy that can be readily observed with many phytoplankton species in laboratory studies. However, it is unclear how these allelopathic interactions are altered when the complexity of the system is increased to more closely mimic natural conditions. In the present study, we conducted laboratory experiments to decipher how the identity, abundance, and growth stage of competitors affect the outcome of allelopathic interactions with the red tide dinoflagellate Karenia brevis. Multiple chemical compounds produced by K. brevis were found to inhibit the growth of 4 phytoplankton competitors, although these competitors were susceptible to different combinations of compounds. We found that physiological state and cell concentration of competitors were important determinants of allelopathy, with early-stage (lag phase) cells more vulnerable to allelopathic effects than later growth stages for the diatom Skeletonema grethae. Despite being allelopathic to multiple competitors in the laboratory, in a microcosm experiment using plankton field assemblages, extracellular extracts of 2 strains of K. brevis had no effects on some taxa although they stimulated the growth of some diatoms. This suggests that in a species-rich ecological community under oligotrophic conditions, the relative importance of K. brevis allelopathy may not be as high as most laboratory studies predict.

KEY WORDS: Allelopathy · Competition · Phytoplankton · Red tide

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Cite this article as: Poulson KL, Sieg RD, Prince EK, Kubanek J (2010) Allelopathic compounds of a red tide dinoflagellate have species-specific and context-dependent impacts on phytoplankton. Mar Ecol Prog Ser 416:69-78.

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