Temperature as a factor regulating growth and toxin content in the dinoflagellate Alexandrium catenella

Controlled laboratory culture of Alexandrium catenella was used to determine the effects of a range of temperatures between 10 and 16 °C on the growth and saxitoxin content of this dinoflagellate, using strain ACC02 isolated from seawater at Aysen, XI Region, Southern Chile. Cell cultures were made using L1 culture medium at 30‰ salinity, and a photon flux density of 59.53 μmol m² s⁻¹. The results showed that the duration of the exponential growth phase was determined by the experimental temperature, with maximum cell concentrations obtained at 12 °C; significantly lower cell concentrations and growth rates were obtained at 16 °C. Cell dry weight and chlorophyll a values followed cell growth trends. The toxicity of A. catenella was variable at all the experimental temperatures, with a tendency towards having an inverse relation to temperature, with the highest values occurring at 10 °C and the lowest at 16 °C. The optimal range of temperature for the growth of the Chilean strain of A. catenella differed from rates reported for this species isolated at other latitudes, and was correlated with natural temperature conditions predominant in the environment from which it was isolated. The inverse relation of toxicity with temperature in the laboratory was broadly reflected in observations on the toxicity of this dinoflagellate in the field, and coincided with results from the literature.