Abstract

Alexandrium affine (Inoue et Fukuyo) Balech, isolated from Bahía Concepción (Gulf of California), was studied to determine the effect of environmental factors on cyst germination and vegetative growth. Alexandrium affine was homothallic and isogamous, and formed cysts in nutrient-deficient (N- or P-limiting) medium. The maturation period of newly formed cysts varied between two weeks and three months, depending on the storage temperature, with colder temperatures prolonging the process. The rate of germination increased with increasing temperature, and was not significantly influenced by light. Germination experiments suggest a broad temperature window for A. affine cysts, ranging from 5 to 25 °C. The optimal vegetative growth rates were 0.25 to 0.34 day⁻¹ at 20–30 °C. No vegetative growth was observed below 15 °C or above 35 °C. With HPLC toxin analyses, we confirm that this species does not produce saxitoxins. These data on the dormancy, excystment, and growth characteristics seem to be regulated by the environmental constraints of this subtropical bay.