ABSTRACT
Copper is an essential micronutrient for living organisms and play a crucial role in enzymatic reactions. Recently the application of copper nanoparticles in many industrial processes leads to the entry of these particles into the nearby aquatic ecosystem. Therefore, the impacts of these nanoparticles on aquatic organisms are of major concern. The present study aims to evaluate the ecotoxicity of both bulk and copper nanoparticles using the freshwater fish Labeo rohita and to provide a comparative toxicity assessment using toxicological endpoints. Fish L. rohita were exposed to different concentrations (20, 50, and 100 µg/L) of bulk copper and copper nanoparticles for a period of 96 h, and ionoregulatory disturbances and gill Na+/K+-ATPase activity were evaluated. After 96 h, the plasma sodium level was significantly (p < 0.05) increased in copper nanoparticle-exposed fish when compared to control fish and bulk copper-exposed fish at 20 µg/L. In contrast, a significant increase was noted in bulk copper-exposed fish at 50 and 100 µg/L. The plasma chloride level was significantly (p < 0.05) increased in bulk copper-treated fish when compared to copper nanoparticles and control fish at 20 µg/L concentration. In 50 µg/L-exposed fish and 100 µg/L-exposed fish, the plasma chloride level was found to be increased in copper nanoparticle-exposed fish. The plasma potassium level was found to be significantly decreased (p < 0.05) in copper nanoparticle-treated fish when compared to bulk copper and control fish at 20 µg/L. However, a significant increase (p < 0.05) in plasma K+ level was observed in copper nanoparticle-treated fish L. rohita when compared with the bulk copper-exposed fish at 50 µg/L and control fish. Fish exposed to bulk copper at 100 µg/L showed a significant decrease (p < 0.05) in plasma K+ level when compared with the 100 µg/L copper nanoparticle-exposed fish and control fish. In this study, gill Na+/K+-ATPase activity was significantly increased (p < 0.05) in all the three concentrations of copper nanoparticles (20, 50, and 100 µg/L) when compared with the control fish and bulk copper-treated fish. The toxicity of both copper nanoparticles and bulk copper significantly differ when compared with the control fish. Further long-term studies are needed to confirm its toxic nature in aquatic organisms.
