Posted September 7, 2012 Atlanta, GA
At the 2012 annual meeting of the International Society of Chemical Ecology in Vilnius, Lithuania, Professor Julia Kubanek delivered an invited lecture sponsored by the society. This award is made each year to a chemical ecologist whose recent work is at the forefront of the field, and is named after the late Milt Silverstein and John Simeone, pioneers of this field and co-founders of the Journal of Chemical Ecology. Professor Kubanek presented "War in the Plankton: Sublethal and reciprocal impacts of red tide algae on competing phytoplankton", co-authored by Georgia Tech current and former students Kelsey Poulson-Ellestad, Jessie Roy, Robert Drew Sieg, Christina Jones, Emily Prince, Tracey Myers, as well as former GT postdoctoral researcher Clare Redshaw, and collaborators Facundo Fernandez (GT), Brook Nunn (University of Washington), Jerome Naar (University of North Carolina at Wilmington), and Mark Viant and Jon Byrne (University of Birmingham UK).
Dr. Kubanek is a Professor in the School of Biology at Georgia Tech. Her invited lecture is described below:
War in the Plankton: Sublethal and reciprocal impacts of red tide algae on competing phytoplankton
How individual species come to be dominant members of marine planktonic communities is not deeply understood; however, it is thought that chemistry plays a substantial role. For example, some red tide-forming dinoflagellates produce toxic secondary metabolites that are hypothesized to enhance dinoflagellate fitness by acting as grazer deterrents, allelopathic agents, or antimicrobial defenses. In field and lab experiments we have shown that the red tide dinoflagellate Karenia brevis is allelopathic, inhibiting the growth of several co-occurring phytoplankton species, but that K. brevis natural products other than well-known brevetoxins are responsible for suppressing most of these species. At least one phytoplankton competitor, Skeletonema costatum, retaliates against K. brevis, reducing its allelopathic effects and degrading waterborne brevetoxins. Several other phytoplankton species also metabolize brevetoxins, removing these toxins from the water column and mitigating the negative effects on invertebrates. Death is a rare outcome of K. brevis allelopathy, with more subtle responses predominating, such as reduced photosynthetic output and increased cell permeability. These changes in cellular metabolism and physiology may be more readily characterized and measured by a systems biology approach than by growth or cell lysis assays. NMR metabolomics has provided preliminary evidence for sub-lethal impacts of exposure to K. brevis allelopathy on the metabolism of neighboring phytoplankton. Future work will expand upon these initial results with mass spectrometry-based metabolomics and proteomics methods, as well as experiments with other vulnerable competing phytoplankton species, with the goal of identifying cellular targets and understanding the molecular mechanisms of red tide allelopathy. Our results indicate that chemically-mediated interactions are reciprocal, and that ecosystem-level consequences of red tides (such as fish kills caused by waterborne toxins) may depend upon which other phytoplankton species are present.