Ecophysiological characterization and toxin profile of two strains of Cylindrospermopsis raciborskii isolated from a subtropical lagoon in Southern Brazil

In the present work, we attempted to characterize two isolates of Cylindrospermopsis raciborskii, LP1 and LP2, from Peri Lagoon, for their morphology, ecophysiology, and toxin profiles. The genetic identity of the isolates was confirmed by amplifying and sequencing 16S rRNA. The isolates showed different morphologies and significant differences in the length of trichomes. LP2 showed a trend for higher growth rates than LP1 at the different temperatures and N:P ratios. Both isolates showed low light requirements, but were able to tolerate irradiances of around 200 mu mol photons m(-2) s(-1). LP2 showed higher concentrations of saxitoxin than LP1 and wider range of analogs, therefore being considered more toxic. These results support the hypothesis of ecotype selection for this species, which probably originated in response to environmental fluctuations in Peri Lagoon. Dominance during almost the entire year can be explained by the alternation of these ecotypes in the total biomass contribution according to their physiological advantages, contributing to the ecological success of this species.