Bioaccumulation of heavy metals and petroleum hydrocarbons in the blue crab (Callinectes sapidus, Rathbun 1896) from Ogu Creek in Upper Bonny Estuary, Nigeria

Abstract

Prolonged industrial and artisanal discharge of petroleum refinery effluents into the Ogu Creek at the Upper Bonny estuary of the Niger Delta could pose a great threat to the aquatic biotopes. This research investigated bioaccumulation of selected heavy metals and petroleum hydrocarbons in the blue crab (Callinectes sapidus) from the creek. Crabs (N=20; average length 18±20cm; weight 150.18±0.02g) were collected with nets. Mean concentrations (mg/l) of Zn (0.044±0.01), Cd (0.002±0.00), Cr (0.001±0.00), Pb (0.001±0.00), Fe (5.82±0.29), Mn (0.001±0.00), total petroleum hydrocarbons (TPH; 40.23±2.83) and total polynuclear aromatic hydrocarbons (ΣPAHs;7.60±1.29) were lower in water than sediments (22.10±1.37, 1.98±0.04, 2.13±0.09, 4.80±0.57, 24.03±1.29, 0.04±0.01, 70.93±3.10 and 29.80±4.02mg/kg, respectively) at the impacted location. Accumulations (μg/g) in digestive tract (dtr), muscle (mus) and ovaries (ov) were as follows: Zn 10.50 (dtr), 11.00 (mus), 2.40 (ov); Cr 0.21 (dtr), 0.10 (mus), 0.04 (ov); Cd 0.01 (dtr), 0.02 (mus), 0.01 (ov); Pb 0.04 (dtr), 0.02 (mus), 0.01 (ov); Mn 0.05 (dtr), 0.03 (mus), 0.01 (ov); TPH 4.14 (dtr), 3.14 (mus), 1.20 (ov); and mononuclear aromatic hydrocarbons (MAHs=BTEX) 0.01μg/g (dtr), 0.02 μg/g (mus), 0.01 μg/g (ov). Accumulations of TPH and BTEX were significantly (p<0.05) higher at the impacted location (p = 0.03 and 0.02, respectively) than reference locations. High TQ/HQ values of 1.59, 2.82 and 1.90 were recorded for Zn, TPHs and PAHs, respectively. The results raise environmental health concerns among consumers of the aquatic food in the area.