Detección de poblaciones tóxicas de Microcystis spp. con distintas preferencias ambientales. Estudio de caso

In this work, the dynamics and toxicity of Microcystis spp. in Salto Grande reservoir (Uruguay river), as well as the genetic diversity of their toxic populations were assessed in winter and summer during 2013. Cell abundance of Microcystis spp. variated amongst different sites and between seasons, showing a signifcantly higher cell and toxic genotype abundances (copies of mcyE gene) and microcystin-LR concentration during summer. Furthermore, when genetic diversity of toxic Microcystis was analyzed by high resolution melting analysis of mcyJ amplicons, two genotypes exhibiting different environmental preferences were detected (cluster 1 and 2). Cluster 1 included samples found at water conditions of low temperature (lower than 17,6 °C) and slightly high conductivity (~52 to 58 µS cm-1), showing small Microcystis abundance and absence of microcystin-LR, whereas cluster 2 comprised samples from higher temperatures (between 17,6 and 25,9 °C) and lower conductivity (~50 to 52 µS cm-1) conditions, and with a higher cell abundance and microcystin-LR production. Our results suggest that toxic Microcystis spp. populations that bloom during summer are different from those that persist during winter and pointed to water temperature and conductivity as relevant variables that control their abundance and toxicity.