Effects of nickel and its combination with other heavy metals (Cd, Pb, Zn) on common carp ( Cyprinus carpio Linnaeus, 1785)

We aimed to study ex-situ the effects of acute toxicity test with Ni 2+ , Ni+Cd, Ni+Pb and Ni+Zn on behavior, survival and oxygen consumption of common carp, Cyprinus carpio L. Behavioral effects were more pronounced in fish exposed to 0.2 mg/l 1 Ni 2+ , 0.3 mg/l Ni 2+ and 0.45 mg/l Ni 2+ . Common stress reactions, such as anxiety, jumps and quick movements, and also accelerated movements of the fish gill covers were observed. Fish behavior from the lower Ni 2+ concentrations (0.05 and 0.1 mg/l Ni 2+ ) and from the test combinations of Ni+Cd, Ni+Pb and Ni+Zn was quite different. In general, during the first hours of the experiment the fish were anxious, but after 48 hours they started to be lethargic, which was expressed in their slow movements. Fish survival was 90% under intoxication with 0.2 mg/l Ni 2+ and combination of Ni+Pb. In the rest of the tested heavy metal concentrations it was 100%. Data on the respiration intensity rate and oxygen consumption of fish exposed to 0.2 mg/l Ni 2+ , 0.3 mg/l Ni 2+ , Ni+Pb and Ni+Cd were lower in comparison with the control group. This result indicated that the Ni 2+ ions impacted the fish respiratory system. Depending on their toxic effect the descending row of the studied heavy metals could be presented as follows: Ni 2+ > Ni+Pb > Ni+Cd > Ni+Zn. Overall, such experiments could be successfully applied in environmental monitoring and risk assessment programs for metalcontaminated aquatic ecosystems and toxic effects on fish.