Changes in antioxidant enzyme activities in the livers and gills of three cyprinids after exposure to a cyanobacterial bloom in the Gruža Reservoir, Serbia

We examined the influence of an Aphanizomenon flos-aquae bloom on the activities of antioxidant enzymes in the livers and gills of three cyprinids, Rutilus rutilus (roach), Blicca bjoerkna (white bream) and Carassius gibelio (Prussian carp) from the Gruža Reservoir (Serbia). We also studied tissue- and species-specific differences in the antioxidant response to the cyanobacterial bloom. The activities of total, copper zinc and manganese containing superoxide dismutases (Tot SOD, CuZn SOD, Mn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and the biotransformation phase II enzyme glutathione-S-transferase (GST) were determined before and during the cyanobacterial bloom. B. bjoerkna exhibited higher antioxidant response to the cyanobacterial bloom than R. rutilus and C. gibelio; liver Tot SOD, CuZn SOD and GST activities increased during the bloom only in this species. Liver Mn SOD activity in all three cyprinids increased during the bloom. A decrease in liver CAT and GSH-Px activities that was detected in all three species may be directly responsible for an enhanced susceptibility of fish to potential oxidative stress caused by the bloom. Tot SOD, CuZn SOD, Mn SOD, GSH-Px, GR and GST activities in gills were also inhibited during the bloom showing that the gills were affected more than the liver. The observed changes in the activities of aforementioned antioxidant enzymes during the cyanobacterial bloom suggest that these parameters could be important biomarkers for ecotoxicological risk in fish that inhabit ecosystems where A. flos-aquae blooms occur.