Assessment of zirconium oxychloride-induced toxicity in Oreochromis niloticus (Linnaeus 1758): from morphological alteration to oxidative stress evaluation.

The accumulation of metal toxicants in aquatic systems has been shown to create a harmful environment for marine life. This study examined the toxic effects of zirconium oxychloride (ZR) using Nile tilapia (Oreochromis niloticus) as a model organism. The fish were exposed to 10 ppm, 20 ppm, 40 ppm, 60 ppm, 80 ppm, 100 ppm, and 200 ppm concentrations of ZR for 45 days. Mortality rates in the treated groups were recorded through survival analysis, revealing a dose-dependent increase in mortality among Nile tilapia exposed to ZR. Behavioural changes were observed across all treated groups compared to the control. Histopathological analysis of gills, liver, intestine, and eye showed altered tissue structure in fish exposed to ZR. Biochemical evaluation of oxidative markers in the liver and intestine was also conducted for the first time in Nile tilapia exposed to ZR. Oxidative damage was detected through lipid peroxidation (LPX) levels, and the response of Nile tilapia to oxidative stress induced by ZR was assessed by examining superoxide dismutase (SOD) activity, catalase (CAT), and reduced glutathione (GSH) levels. Elevated LPX levels, along with increased activity of SOD, CAT, and GSH, were detected in the liver and intestines of all treated groups in a dose-dependent manner. These findings may help evaluate ZR toxicity in freshwater fish, especially in mining areas, and underscore the need for further research into the mechanisms of ZR-induced oxidative stress.