The effect of sub-lethal exposure to copper and the time course of recovery in clean water on biochemical changes in juvenile fish (Acipenser persicus)

This study reports the 96-h LC50 value and tissue copper (Cu) levels and biochemical changes in juvenile fish (Acipenser persicus) exposed to 0.026 mg/l ambient Cu for 1, 7 and 14 days. It then examined the recovery of the same parameters after placing the juvenile fish in clean water for a further period of 28 days. The intestine, kidney and gill Cu levels, plasma glucose, total protein, triglyceride, cortisol, triiodothyronine and thyroxine concentrations, liver protein contents, liver catalase, superoxide dismutase (SOD) and glutathione S-transferase activities were studied. The 96-h LC50 value of Cu was 0.502 mg/l for juvenile A. persicus. The results indicate that Cu exposure produced significant accumulations of Cu in gills and kidney over the treatment time. Sublethal dose of Cu resulted in a short-term increase in plasma glucose, total protein and cortisol levels that decreased with time. After the 28-day recovery phase, there were significant differences in kidney Cu levels and triglyceride concentrations as well as SOD activities between recovery fish treatments and their control groups on day 42. The 28-day recovery phase caused significant decreases in total protein levels and SOD activities of Cu-exposed fish on day 42 compared to day 14. The results suggest that 28 days are insufficient for complete recovery to Cu exposure by juveniles and a longer period would be required for full recovery. Moreover, the study showed that the recovery phase following Cu exposure could change biochemical parameters to levels that are not close to those seen during exposure or control levels.