Oxidative stress biomarkers are modulated in silver carp (Hypophthalmichthys molitrix Val.) exposed to microcystin-producing cyanobacterial water bloom

Abstract

In the present paper we evaluated the effects of natural toxic cyanobacterial water bloom on oxidative stress biomarkers in silver carp. Modulations of reduced gluthatione (GSH), an important cellular antioxidant and substrate of detoxification enzymes and malondialdehyde (MDA), a biomarker of lipid peroxidation, were monitored in three groups of fish. The groups were as follows: 1) fish from aquarium, 2) fish from store-pond without cyanobacterial bloom, and 3) fish exposed for 25 days to living natural population of cyanobacterial water bloom (dominated by the populations of colonial cyanobacteria Microcystis ichthyoblabe (60%) and Microcystis aeruginosa (40%) containing microcystins at the total concentration 513 μg·g -1 of dry biomass). In comparison with control fish from the store-pond, the levels of GSH were significantly elevated in fish exposed to cyanobacteria indicating increased GSH demand as a result of oxidative stress and/or induction of detoxification enzymes in microcystin-exposed fish. On the other hand, fish from aquarium had significantly lower levels of GSH in comparison with those from the store-pond. The concentrations of MDA were slightly elevated in fish exposed to cyanobacteria, differences between fish groups were not statistically significant. Our observations indicate that exposure of fish to toxic cyanobacterial blooms induces oxidative stress, a fundamental factor of numerous diseases and accelerated ageing in living organisms.