TOXICITY OF ROAD RUNOFF CHEMICALS TOWARDS COMMON CARP (Cyprinus carpio)

Abstract

Road related contaminants are considered as a significant source of pollution, however there are only few studies conducted on the toxicity of road runoff on fresh water fish species. Fish in aquatic environment are considered as valuable indicator of aquatic pollution. This study evaluates the exposure to environmentally realistic concentrations of chromium (Cr) and cadmium (Cd) and its responses in juveniles of Common carp (Cyprinus carpio). To understand the toxicity of road runoff, leaching experiment was conducted to simulate road runoff processes using road dust samples. Common carp was exposed in a semi static exposure system at environmentally realistic concentrations of Cr and Cd separately and in combination. Exposure concentrations for Cr, Cd and mixture of Cr-Cd were maintained at 0.2, 2 mg/L for Cr and 0.05, 0.1 mg/L for Cd and 2 + 0.1 mg/L for Cr-Cd mixture for 45 days. The experiment was conducted in two different water qualities in two batches and toxicity of Cr and Cd was assessed by using set of biomarkers such as haematological parameters, erythrocytes nuclear and cellular abnormalities and uptake in gills tissue. In the first batch of experiment, haematological results of Common carp revealed that exposure of Cr resulted significant (p<0.05) decrease in red blood cell (RBC) count, haemoglobin (Hb), haematocrit (HCT) content and significant (p˂0.001) decrease in mean corpuscular haemoglobin concentration (MCHC), however, significant (p<0.01) increase in white blood cell (WBC) count and significant (p<0.05) increase in mean corpuscular volume (MCV) was observed among treatment groups. The frequency cellular and nuclear abnormalities in erythrocytes of Common carp revealed genotoxicity with the total percentage abnormalities of 16%, 25.6% and 66% exposed to 0.2, 2 and 17 mg/L Cr concentrations as compared to total abnormalities in control group i.e. 5.6%. The accumulation of Cr significantly (p<0.001) increased in gills when exposed to Cr test concentrations (0.2, 2 and 17 mg Cr/L). In the Second batch of experiment, exposure of Cr, Cd and mixture of Cr-Cd resulted in significant (p<0.05) decrease in RBC count, Hb, HCT concentration and significant (p>0.05) decrease in MCV whereas, significant increase (p<0.05) in WBC count and MCHC was found. Changes in haematological indices revealed that Common carp exposed to Cr and Cd was under stress. Nuclear and cellular abnormalities in erythrocytes of Common carp revealed genotoxicity of Cr and Cd even at the lowest concentrations (0.2 mg Cr/L and 0.05 mg Cd/L). The frequency of cellular and abnormalities in erythrocytes of Common carp revealed that maximum frequency of total abnormalities observed was 51.6% in mixture of Cr-Cd followed by total abnormalities of 24.6 and 26.3% for 0.2, 2 mg/L Cr concentration, 19.3% and 23.7% for 0.05, 0.1 mg/L Cd as compared to control i.e. 8.6%. The uptake of Cr in gills tissues increased significantly (p<0.001) at test concentrations singly (0.2, 2 mg Cr/L) and significantly (p<0.01) increased in mixture of Cr and Cd (2 + 0.1 mg/L Cr-Cd) whereas, exposure to Cd singly at a concentrations (0.05, 0.1 mg Cd/L) resulted slightly increase (p<0.05) uptake in gills however, Cd uptake in gills slightly decreased (p<0.05) when exposed to mixture of Cr and Cd. The present study gives insight of the probable harmful effects of road related contaminants to fresh water bodies.