Effects of Water-Borne Mercury and Cadmium Exposure on Lipid Peroxidation and Antioxidant Enzymes in Mangrove Red Snapper <em>Lutjanus argentimaculatus</em>

Abstract

Effects of waterborne cadmium (Cd 2+ ) and mercury (Hg 2+ ) both separately and in combination on the lipid peroxidation and antioxidant activity in Lutjanus argentimaculatus was investigated. The fish was exposed for 3, 7 and 15 days respectively to Cd 2+ , Hg 2+ and the mixture of both. Exposure to Cd 2+ was done at three different concentrations viz 1, 5 and 100 µg/L .The fish was exposed to Hg 2+ at 0.2，0.5 and 10 µg/L. Further L. argentimaculatus was also exposed to a mixture containing 5 µg/L Cd 2+ and 0.5 µg/L Hg 2+ . The results showed increased levels of antioxidant enzymes such as Superoxide Dismutase (SOD), Catalase (CAT) and Peroxidase (POD) (p<0.05) both in hepatic and branchial tissues. The level of Malonialdehyde (MDA) which is an indicator of lipid peroxidation also showed significant increase (p<0.05). Further, antioxidant enzymes and MDA could not fall down to normal levels even after 15 days of release to clean sea water in all the treatments tested. However, the activity of antioxidant enzymes in the fishes exposed to mixture containing both Cd 2+ and Hg 2+ did not showed remarkable raise as when treated separately. The study indicated that the increase of antioxidant enzymes activity and MDA need to be considered carefully as pollution indicators as their values do not conform well to the corresponding metal ion concentrations, in view of co-effects of metals.