Acute and sublethal effects in an Indian major carp Cirrhinus mrigala exposed to silver nitrate: Gill Na+/K+-ATPase, plasma electrolytes and biochemical alterations

Due to prolonged use of silver in many applications, it enters into the freshwater and affects the aquatic organisms. Fingerlings of Cirrhinus mrigala were exposed to acute and sublethal concentrations of silver nitrate and the alterations of gill Na(+)/K(+)-ATPase, plasma electrolytes and biochemical parameters were assessed. The median lethal concentration of silver nitrate to the fish C. mrigala for 96 h was found to be 0.107 mg/l (with 95% confidence limits). 1/10th of LC 50 96 h value (0.0107 mg/l) was selected for sublethal study. During acute treatment branchial Na(+)/K(+)-ATPase activity was inhibited approximately 44.34% after 96 h of exposure. In sublethal treatment, silver nitrate could not produce a significant change in the activity of the enzyme at the end of 7th day. However, after 14th day, significant (p < 0.05) decrease was noted showing 22.52%-49.11% in rest of the study period. Silver intoxication resulted hyponatremia, hypokalemia, hypochloremia, and hypoproteinemia in both the treatments. Despite the decrease in these parameters, plasma glucose level was found to be increased in both the treatments to endure the silver toxicity. We suggest that the alterations in branchial Na(+)/K(+)-ATPase activity, plasma electrolytes, and biochemical parameters of fish may be useful in environmental biomonitoring and to assess the health of fish in freshwater habitat contaminated with silver.