Abstract

In the last decades, climate change has been one of the key pieces in the increase of the frequency, intensity, spatial-temporal distribution and composition of the Harmful Algal Blooms (HABs) worldwide, affecting the physiology and toxicity of the microalgae involved in these outbreaks. The fjords and channels ecosystem from southern Chile (48-56ºS) has historically presented blooms of toxic species that produce a wide variety of toxins (PSP, DSP, ASP, among others), becoming a very vulnerable system to environmental changes. We present here preliminary studies of the potential effect of future increases in carbon dioxide (pCO2) on the growth rate and toxin production of the PST producer Alexandrium catenella. Batch cultures of A. catenella (strain M7 isolated from isla Crossover, 49ºS) were grown in short-term experiments under the combination of 2 pCO2 levels (415 and 1200 ppm) and pH ranges from 7.31 to 8.01, comparable values to present days and supposed future levels, respectively. We observed differences between the treatments on the growth rate and toxin production, with effects of both pCO2 and pH on the cultures. Our data showed a relationship between the specific growth rate and the impact of pCO2 on growth, were the A. catenella cultures were positively affected to increased pCO2. The toxin composition was also altered by the increased pCO2 supply, resulting in a promotion of PST production. This is the first evidence that toxin production by a sub Antarctic strain of A. catenella is sensitive to changes in atmospheric pCO2 levels. Further studies will be necessary to assess whether other strains of A. catenella and others toxic dinoflagellates species from southern Chile has similar responses to this climate stressors; the eventual consequences of an expansion of the blooms and increase in toxicity under increased pCO2, for the fjords and channels system of southern Chile, are also discussed.