Intracellular microcystins degradation and acute toxicity decrease towards Daphnia similis by low electron-beam irradiation doses

Abstract

Ionizing radiation has attracted attention due to its ability to inhibit pathogens and microorganisms, with low doses reported as being able to degrade cyanotoxins and inhibit toxic cyanobacteria growth. In this context, the aim of the present study was to investigate how electron beam irradiation (EBI) applied at doses between 1 and 10 kGy affect intracellular and extracellular microcystin variants. Effects on M. aeruginosa culture recovery, as well as changes in physico-chemical cyanobacterial suspension parameters and water quality alterations were assessed through ecotoxicity assays. The findings indicate that doses over 2 kGy may are lethal to M. aeruginosa even at 48 h post-irradiation. Concerning physico-chemical parameters, exposure to 2–5 kGy doses decrease pH values and later stabilizing. At least 50 % of intracellular MC led to significant degradation of all variants at 3 kGy. No acute toxicity effects were observed in Daphnia similis exposed to sample supernatants. Statistically significant differences were observed when cladocerans were exposed to M. aeruginosa cells treated with EBI doses ranging from 3 to 10 kGy compared to non-treated cyanobacterial suspensions. These findings suggest that low EBI radiation doses are suitable for the control of toxic cyanobacteria in water treatment processes, providing a less toxic environment compared to non-treated solutions.