Effect of temperature on growth and paralytic toxin profiles in isolates of Gymnodinium catenatum (Dinophyceae) from the Pacific coast of Mexico.

The effects of temperature on growth, cell toxicity, toxin content, and profile of paralytic shellfish toxins was determined in eight isolates of Gymnodinium catenatum from several localities along the Pacific Coast of Mexico. The isolates were cultivated in modified f/2 media with Se (10(-8) M), and a reduced concentration of Cu (10(-8) M), under a 12 h:12 h day-night cycle with an irradiance of 150 μE m(-2) s(-1). Isolates were progressively adapted for three generations to each of the temperatures (16, 19, 22, 24, 27, 30, and 33 °C). The cultures were grown in 125 mL Erlenmeyer flasks with 60 mL of media and harvested by filtration in late exponential growth. Toxins were analyzed by HPLC with a post-column oxidation and fluorescent detection (FLD). G. catenatum isolates tolerate temperatures between 16 and 33 °C, with maximum growth rates of 0.32 and 0.39 div day(-1) at 21 °C and 24 °C, respectively; maximum cell densities of 4700 and 5500 cells mL(-1) were obtained at 27 and 21 °C, respectively. No effect of toxicity per cell with temperature was observed, varying between 10.10 and 28.19 pgSXTeq cell(-1). Ten saxitoxin analogues were detected in all isolates, observing changes in the toxin profile with temperature. C1/2 toxins decreased from 80% mol at 16 °C to 20% mol at 33 °C, B1/2 toxins increased from 19% mol at 16 °C to 42% mol at 33 °C, and decarbamoyl toxins were more abundant at 21 °C. These results show that G. catenatum isolates from different regions of the Pacific coast of Mexico have a similar response to temperature and that this parameter can modify growth rate, cell density, and toxin profile of the species, particularly the decarbamoyl and sulfocarbamoyl toxins.