Increasing atmospheric CO2 is promoting ocean acidification and higher global temperatures and has been suggested as a possible factor for shifts in marine phytoplankton composition to more harmful species. Karenia brevis is the major harmful algal species in the Gulf of Mexico producing potent neurotoxins known as brevetoxins. We examined how changes in ocean inorganic carbon chemistry associated with pre-industrial (250 ppm), recent (350 ppm), and predicted at 2100 (1000 ppm) pCO2 levels and increased temperature affect growth rates and brevetoxin production in K. brevis. At the predicted pCO2 levels for 2100, growth rate of K. brevis Wilson clone increased substantially by 46% at 25 °C (0.43 ± 0.01 d−1) compared to recent and pre-industrial levels (0.29 ± 0.01 d−1). Growth rates also increased for a low brevetoxin-producing clone, SP1, from 0.24 ± 0.02 d−1 at lower pCO2 levels to 0.33 ± 0.003 d−1 at a pCO2 of 1000 ppm. When grown at a higher temperature (30 °C), growth rates for the Wilson clone significantly decreased at all three pCO2 by approximately 30%. However, even at the higher temperature, K. brevis growth rate significantly increased by 30% (0.30 ± 0.01 d−1) at the 1000 ppm CO2 level when compared to recent and pre-industrial CO2 levels (0.21 ± 0.01 d−1). Although K. brevis growth rate decreased at higher temperatures, the growth rate at pCO2 level of 1000 and 30 °C was slightly higher than at current conditions (pCO2 level of 350 and 25 °C). Modification of pCO2 levels and temperatures did not have an effect on total brevetoxin production or brevetoxin profiles in either clone examined. Due to the increased growth rate, total brevetoxin production was significantly higher at the pCO2 level of 1000. Finally, from these results we conclude there is no connection between growth rate and brevetoxin per cell. Although neither pCO2 nor temperature influenced brevetoxin production per cell, we suggest that under predicted future climate conditions K. brevis blooms have the potential to produce higher cell concentrations and increased brevetoxin concentrations, which will pose an increased risk for ecosystem and human health.
Errera R. M., Yvon-Lewis S., Kessler J. D. & Campbell L., 2014. Reponses of the dinoflagellate Karenia brevis to climate change: pCO2 and sea surface temperatures. Harmful Algae 37:110–116. Article (subscription required).
