RESUMO
This research reports the presence of species Cylindrospermopsis raciborskii and cylindrospermopsin (CYN) in the Huong River and the relationship between species with environmental factors to find a scientific basis for predicting the risk of pollution of the species and CYN in waters. Strains of C. raciborskii isolated from the river were also identified as potentially toxin-producing through the determination of the presence of toxins in the cultures by ELISA; the presence of the genes involved by PCR confirms the CYN-producing ability of species C. raciborskii from this water body. Our results have confirmed the presence of toxic cyanobacteria C. raciborskii in the Huong River. C. raciborskii from the Huong River are mostly solitary, straight trichomes. Analyses of all C. raciborskii strains from the Huong River by ELISA for cylindrospermopsin were positive. The contents of cylindrospermopsin (CYN) in each strain were different, ranging from 5.25 ng mg-1 wet weight in CR1DD to 70.83 ng mg-1 wet weight in CR1NY. PCR analysis confirmed that the genes involved in the production of this cyanotoxin were present in C. raciborskii. The relationship between densities and toxicity showed a correlation coefficient R of 0.88. This was a relatively high positive correlation index, indicating the close links between densities and toxins: toxin CYN concentrations increased when C. raciborskii densities increased.