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NITROGEN LIMITATION INCREASES BREVETOXINS IN KARENIA BREVIS (DINOPHYCEAE): IMPLICATIONS FOR BLOOM TOXICITY1
Article first published online: 7 JUN 2012
© 2012 Phycological Society of America
Journal of Phycology
Volume 48, Issue 4, pages 844–858, August 2012
How to Cite
Ransom Hardison, D., Sunda, W. G., Wayne Litaker, R., Shea, D. and Tester, P. A. (2012), NITROGEN LIMITATION INCREASES BREVETOXINS IN KARENIA BREVIS (DINOPHYCEAE): IMPLICATIONS FOR BLOOM TOXICITY. Journal of Phycology, 48: 844–858. doi: 10.1111/j.1529-8817.2012.01186.x
Received 27 September 2011. Accepted 1 May 2012.
- Issue published online: 1 AUG 2012
- Article first published online: 7 JUN 2012
- Accepted manuscript online: 7 MAY 2012 11:43AM EST
- carbon:nutrient balance hypothesis;
- cellular volume;
- harmful algal blooms (HAB);
- Karenia brevis;
- nitrogen limitation;
Laboratory and field measurements of the toxin content in Karenia brevis cells vary by >4-fold. These differences have been largely attributed to genotypic variations in toxin production among strains. We hypothesized that nutrient limitation of growth rate is equally or more important in controlling the toxicity of K. brevis, as has been documented for other toxic algae. To test this hypothesis, we measured cellular growth rate, chlorophyll a, cellular carbon and nitrogen, cell volume, and brevetoxins in four strains of K. brevis grown in nutrient-replete and nitrogen (N)-limited semi-continuous cultures. N-limitation resulted in reductions of chlorophyll a, growth rate, volume per cell and nirtogen:carbon (N:C) ratios as well as a two-fold increase (1%–4% to 5%–9%) in the percentage of cellular carbon present as brevetoxins. The increase in cellular brevetoxin concentrations was consistent among genetically distinct strains. Normalizing brevetoxins to cellular volume instead of per cell eliminated much of the commonly reported toxin variability among strains. These results suggest that genetically linked differences in cellular volume may affect the toxin content of K. brevis cells as much or more than innate genotypic differences in cellular toxin content per unit of biomass. Our data suggest at least some of the >4-fold difference in toxicity per cell reported from field studies can be explained by limitation by nitrogen or other nutrients and by differences in cell size. The observed increase in brevetoxins in nitrogen limited cells is consistent with the carbon:nutrient balance hypothesis for increases in toxins and other plant defenses under nutrient limitation.