Effects of the algicides CuSO4 and NaOCl on various physiological parameters in the harmful dinoflagellate Cochlodinium polykrikoides

Abstract

The marine dinoflagellate Cochlodinium polykrikoides has spread worldwide and is responsible for harmful algal blooms. The chemical biocides, copper sulfate (CuSO4) and sodium hypochlorite (NaOCl), are known to be effective in removing bloom-forming or biofouling organisms. Here, we assessed the biocidal efficiency and toxicological properties of NaOCl and CuSO4 on the physiological and catalase responses of C. polykrikoides. The endpoints used were cell counts, pigment content, chlorophyll autofluorescence (CAF), and antioxidant catalase (CAT) activity. The test organism showed a dose-dependent decrease in growth rate against the algicides; 72-h median effective concentrations (EC50) were 0.584 and 0.633 mg L–1 for NaOCl and CuSO4, respectively. The decrease in pigment levels and CAF intensity showed that NaOCl and CuSO4 might affect the photosynthetic processes of the exposed cells. Furthermore, a considerable increase in CAT activity in the cells was detected, indicating that the algicides might generate reactive oxygen species, thereby markedly damaging the cells. These results suggest that the test algicides are very effective in removing C. polykrikoides by inducing cellular stress and inhibiting cell recovery at higher concentrations.