RESUMO
Short-term (12-48 h) experiments were carried out to examine the effect of anthracene (three-ring aromatic hydrocarbon), cadmium (CdCl(2)), and chloridazone (triazine herbicide), individually and in combination, on growth and SOD activity of three green algae Scenedesmus: S. subspicatus, S. obliquus, and S. microspina, grown in a batch-culture system. The relative toxicity of chemicals to algae was anthracene > chloridazone >> cadmium. The species revealed similar growth sensitivity to individual chemicals after 24 h of exposure but there were differences between them when exposed to their combinations. Two methods were used to determine the modes of interaction effects of the chemical combinations; both led to the same results, with two exceptions of all 36 variants examined. In general, mixtures of two and three chemicals behaved toward algal growth mainly in an antagonistic manner (20 cases), whereas additive and synergistic interaction occurred 13 and 3 times, respectively. Antagonism was the most frequently observed to growth of S. obliquus; antagonistic interaction and additive effect was noted in relation to S. subspicatus, while response of S. microspina depended markedly on applied combination. There is a relationship between SOD activity and growth response to stress. The markedly higher level of SOD isoforms activities was noticed in cells (especially S. microspina and S. obliquus) exposed to 12 h to combined chemicals, as compared to individually treated and control cells. SOD activities in cells of three Scenedesmus grown 24 h were similar in all experimental variants and after 48 h of exposure significantly decreased in almost all cases (especially in S. subspicatus). There were no differences observed between SOD profiles obtained for all variants examined. Chloroplasts seems to be the main target site of interaction effects of dissimilarly acting chemicals.
