Margarita Esmeralda Gonzales Ferrazi defended her doctoral thesis on toxic cyanobacteria in Lakes Peipsi and Võrtsjärv

The supervisors were researchers Helen Agasild and Kristel Panksep and Professor Tiina Nõges from the Estonian University of Life Sciences. The opponent was Professor Inta Dimante-Deimantovica from the Aquaculture Innovation Infrastructure Centre in Latvia.

The cyanobacterial genus Microcystis is one of the main causes of freshwater blooms and cyanotoxin poisonings worldwide. Due to eutrophication and climate change, blooms caused by toxic cyanobacteria are becoming an increasingly serious problem. They affect aquatic food webs, cause poisoning of aquatic organisms, and limit human use of water bodies.

In her doctoral research, Gonzales Ferrazi investigated the occurrence of potentially toxin-producing Microcystis in lakes Peipsi and Võrtsjärv and its relationships with the lakes’ food webs. To detect the production potential of the toxin microcystin, she used analysis of the mcyE gene.

The results showed that low water temperature does not prevent the presence of potentially toxic strains and that microcystin production may occur year-round. Studies revealed that all major crustacean zooplankton species in Lake Peipsi consume toxic Microcystis, indicating the potential transfer of toxins within the lake’s food web.

The doctoral thesis highlights that risk assessments of toxic cyanobacteria should also take into account the seasonal dynamics of zooplankton. Further studies in lakes Peipsi and Võrtsjärv should focus on direct measurements of microcystin concentrations to more precisely assess its impact on lake food webs.

The doctoral thesis is available in the digital archive of the Estonian University of Life Sciences (EMÜ DSpace)link opens in new page.