Abstract

In order to find the mechanism of destruction of the vegetative cells of A.lexandrium catenella, to prevent the dispersion of this microalgae from geographical areas with high cells concentrations to free zones, experiments were carried out under laboratory conditions, allowing to determine the concentration of hydrogen peroxide and chlorine dioxide generated in situ and the dose of ultraviolet radiation with algicidal effect. A culture of A. catenella at a concentration of 2.000 cells mL-1 were assay to the following treatments: 4 concentrations of hydrogen peroxide (100, 200, 400 and 800 ppm) for 30 minutes; 5 concentrations of chlorine dioxide generated in situ (5, 20, 30., 50 and 75 ppm) for 2.5 and 5 minutes; and 7 doses of ultraviolet radiation, 9, 25, 37, 65, 122, 160 and 172 mJ cm-2. Once the treatments were finished, the cultures were placed in flasks with culture medium, and kept in optimal growth conditions for 21 days. The parameters used to evaluate the algicidal effect on A. catenella were the growth rate, the maximum cells concentration and morphology of the cells. The concentrations and UV doses that produced negative growth rates and cellular destruction were: 200, 400 and 800 ppm for 30 minutes of hydrogen peroxide; 20, 30, 50 and 75 ppm for 2.5 and 5 minutes of chlorine dioxide; 160 and 172 mJ cm-2 of ultraviolet radiation. Despite these results, similar experiences should be evaluated in the field, to know its effects on real scales, i.e. in the fish tanks of the ships that serve for the aquaculture activity (wellboat) and in the salmon processing plants