Assessment of the Toxic Effect of Mixed Effluents from Trans-Amadi Industrial Layout on Tilapia (Oreochromis Niloticus) in Okrika River, Port Harcourt, Rivers State, Nigeria

Abstract

The toxic effect of the mixed effluent (industrial, domestic and municipal) discharged into Okrika River on Tilapia (Oreochromis niloticus) was assessed. Tilapia samples were collected at about 500 meters from point of entry of mixed effluent into the River (downstream) and about 1.5 kilometers from the point of entry of mixed effluent into the River (upstream) while Tilapia from a fish pond affiliated to Rivers State Sustainable Development Authority (RSSDA) was used as control. Malondialdehyde (MDA) concentration and glutathione S-transferase (GST) activity were assayed in the liver homogenate. Alanine amino transferase, ALT; Alanine aspartate transferase, AST and Alkaline phosphatase, ALP were investigated in the fish blood serum. Histopathologic section of the liver was also examined. Results showed that liver MDA concentration increased significantly (p<0.05) in downstream samples (2.45 ± 0.77 to 6.09 ± 1.57nm/mg tissue) with no significant change in upstream liver MDA.   Also, the Hepatic GST was significantly increased in downstream (5.59 ± 1.09 to 16.80 ± 0.71 IU/L) as well as significant decrease upstream (5.59 ± 1.09 to 3.65 ± 1.48 IU/L) in comparison with the control.  ALT, AST, ALP activities in the exposed fish serum showed marked increases downstream (ALT: 99.8 ± 3.5 IU/L; AST: 277.02 ± 39.8 IU/L; ALP: 40.38 ± 11.4 IU/L) at P<0.05 when compared to the control (ALT: 77.8 ± 14.3 IU/L; AST: 150.8 ± 50.7 IU/L; ALP: 15.34 ± 5.6 IU/L). Histology of the liver showed vacuolar degeneration, focal areas of necrosis and aggregation of inflammatory cells between the hepatocytes. This study elucidates negative biochemical changes on the metabolism of the fish due to the presence of mixed effluent in the River.

Keywords: Toxicity, Histopatology, Tilapia, Effluent and Glutathione S-transferase