CO2 and phosphate availability control the toxicity of the harmful bloom dinoflagellate Karlodinium veneficum

We demonstrated that the toxicity of the harmful bloom dinoflagellate Karlodinium veneficum is regulated by both CO2 concentrations and phosphate availability. Semi-continuous cultures were grown in a factorial experiment under all combinations of 3 CO2 levels (230, 430 and 745 ppm) and 2 phosphate conditions (0.5 and 20 µM). After steady-state acclimation was achieved, karlotoxin cellular quotas and growth rates were determined in all 6 treatments. This strain produced both types of karlotoxin, KmTx-1 and KmTx-2. Chlorophyll a-normalized production of the 2 types of karlotoxins was much higher in P-limited cultures compared with P-replete ones under the same CO2 conditions. Increasing CO2 strongly stimulated production of KmTx-1 and decreased production of KmTx-2 in both treatments, but especially in P-limited cultures. Because the KmTx-1 toxin is an order of magnitude more potent than KmTx-2, total cellular toxicity was increased dramatically at high pCO2, particularly in P-limited cultures. Specific growth rates were accelerated by enriched CO2 in P-replete cultures, but not in P-limited treatments. Growth rates or toxicity of K. veneficum could increase substantially in the future with high CO2 levels in the ocean, depending on P availability, and so interactions between rising CO2 and eutrophication could cause major shifts in present day patterns of harmful algal toxin production. These results suggest that over the coming decades, rising CO2 could substantially increase karlotoxin damage to food webs in the often P-limited estuaries where Karlodinium blooms occur.

Fu, F. X., Place, A. R., Garcia, N. S., & Hutchins, D. A., 2010. CO2 and phosphate availability control the toxicity of the harmful bloom dinoflagellate Karlodinium veneficum. Aquatic Microbial Ecology 59(1):55-65. Article (subscription required).


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