BIOCHEMICAL STUDIES ON EFFICACY OF CRUDE OIL BIOREMEDIATION TECHNIQUE ON THE LIVER OF JUVENILES AFRICAN CATFISH (Clarias gariepinus)

Abstract

Crude oil spill threatens water and a wide range of subsurface aquatic organisms including fishes. The objective of this study was to investigate the effect of crude oil exposure at different concentration (ranging from 0.5- 0.9 % (v/v) on biochemical and histological analyses were carried out on the liver of African catfish fingerlings (Clarias gariepinus) with average weight of 17.23±2.80g. In addition haematological parameters of the fish such as plate count volume, white blood cell count, haemoglobin were determined. Sublethal toxicity (96 hour LC50) concentration of crude oil was determined. Mortality was used as criterion of toxicity during the experiment (which was done in duplicates for each test concentration). The efficacy of bioaugmentation as crude oil bioremediation technique was assessed by introducing 10% mixed bacteria culture (Bacillus sphaericus and Alcaligenes eutrophus) into crude oil polluted water, and the biochemical, histological and haematological parameters were determined at the end of 96 hour treatment period. The activities of superoxide dismutase, catalase and level of glutathione decreased significantly (p<0.05) while lipid peroxidation increased significantly (p<0.05) as the concentration increased. Significant decrease (p<0.05) was observed in the haematological parameters; packed cell volume, red blood cell and haemoglobin while significant (p<0.05) increase in white blood count was observed at the end of 96 hour exposure time. Histological studies of the liver showed a varying degree of alteration of the architectural arrangements of the organ following exposure to different crude oil concentration. Following bioaugmentation treatment, the activities of superoxide, catalase and level of reduced glutathione decreased insignificantly (p>0.05) while lipid peroxidation decreased significantly (p>0.05). There was no significant decrease (p>0.05) of haematological parameters (packed cell volume, red blood cell and haemoglobin) while there was no significant (p>0.05) increase in white blood count at the end of 96 hour exposure time. Histological studies of the liver showed normal architectural arrangements of the organ. These results show that bioaugmentation is an effective bioremediation technique for overcoming oxidative stress in fish exposed to crude oil.