Bioaccumulation of Persistent Environmental Pollutants (PEPs) in the Mud Catfishes (Clarias gariepinus and Heterobranchus longifilis) from the Ogu Creek, Rivers State, Nigeria

The long-term discharge of poorly treated petroleum refinery effluent into the Ekerekana Creek, proximal to the Ogu Creek in Ogu, Rivers State, Nigeria, as well as contributions from artisanal refining have created worries about safety to health of consumers of the catfish delicacies, Clarias gariepinus and Heterobranchus longifilis from this coastal water. This research investigated the presence and levels of trace elements (Zn, Cr, Cd, Pb, Mg, Ca, K, Na, Fe and Mn) and hydrocarbons (Total Petroleum HydrocarbonTPHs, Benzene, Toluene, Ethylbenzene and Xylenes-BTEX, and Polycyclic Aromatic Hydrocarbons-PAHs) and Phenol in tissues of the fishes. In C. gariepinus, mean maximum accumulations in mg/kg were as follows: Mg 15.01±2.38 (muscle), Zn 10.25±2.62 (muscle), Fe 9.51±0.53 (gills), K 7.01±0.88 (muscle), Ca 0.42±0.05 (muscle), Pb 0.06±0.01 (muscle), Mn 1.58±0.45 (liver), TPH 6.65±0.42 (muscle), PAHs 0.24±0.05 (muscle), BTEX 0.07±0.01 (muscle) and Phenol 0.007±0.001 (muscle). In H. longifilis, accumulations in mg/kg were as follows: Mg 17.21±1.84 (muscle), Zn 11.27±2.49 (muscle), Fe 11.39±1.64 (gills), K 7.66±1.24 mg/g (muscle), Cd 0.47±0.043 mg/g (muscle), Pb 0.056±0.006 mg/g (muscle) and Mn 1.16±0.268 (liver), TPH 8.69±0.60 (muscle), PAHs 0.49±0.085 (muscle), BTEX 0.09±0.005 (muscle) and Phenol 0.0016±0.0003 (muscle). The accumulations of Cd, Pb, Mg, Ca, K, Na, Fe and Mn in C. gariepinus (Sig. values=0.001, 0.002, 0.011, 0.003, 0.004, 0.008, 0.000, 0.025 respectively) and those of Zn, Cd, Pb, Mg, Ca, K, Na, Fe and Mn (Sig. values=0.024, 0.000, 0.002, 0.002, 0.002, 0.008, 0.024, 0.005, 0.012 respectively) in H. longifilis differed significantly between tissues from impacted and reference locations at p<0.05. TQ/HQ values of, especially Cd and Zn were high (6.80-11.00 and 1.38-3.24 respectively) and exceeded regulatory limits in both fish species.