Physico-Chemical Evolution, Gill Mda Concentration And Histology Of Tilapia Exposed To Mixed Effluent In Okrika River, Rivers State, Nigeria

Abstract

The physico-chemical evaluation and histological studies on Tilapia (Oreochromis niloticus) exposed to mixed effluent (industrial, domestic and municipal) from Okrika River were investigated. 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 was assayed in the gill homogenates in the Tilapia fish blood serum.

It was observed that the biological oxygen demand (BOD), total dissolved solids (TDS), total suspended solids (TSS), conductivity, chromium and cadmium were significantly higher in concentrations in the Okrika River exceeding FEPA regulations in Nigeria. Aside chromium whose concentration was more upstream of the river, BOD, TDS, TSS, conductivity and cadmium show more concentration downstream of the river. Results showed an increase in gill MDA concentration upstream samples (0.00±0.00 to 1.51± 0.24nm/mg), downstream samples (1.51±0.24 to 2.32±0.66nm/mg) and the control samples (2.32±0.66 to 2.70±0.89nm/mg). No significant change was also observed in gill MDA concentration of both downstream and upstream samples when compared with the control. Histology of the gill showed vacuolar degeneration, focal areas of necrosis and aggregation of inflammatory cells between the hepatocytes. From the investigation, the mixed effluents discharged into the river are toxic to the marine environment.

Key words:  Physico-chemical, Histological, Effluent, Malondialdehyde and Tilapia.