Bioaccumulation of Total Hydrocarbon and Heavy Metals in Body Parts of the West African Red Mangrove Crab (Goniopsis pelii) in the Niger Delta, Nigeria

Abstract

This study is based on bioaccumulation of total hydrocarbon (THC) and heavy metals in body parts of the West African red mangrove crab (G. pelii), which inhabit polluted mangrove forests. Thirty crabs were captured in October, 2018 and sorted into male and female. Their lengths and widths were measured, and body parts dismembered and oven-dried at 70 ͦ C for 48 hours. Physicochemical analysis for Cadmium (Cd), Zinc (Zn), Lead (Pb) and THC was measured by spectrophotometric method using HACH DR 890 colorimeter (wavelength 420 nm) and microwave accelerated reaction system (MARS Xpress, North Carolina) respectively. There was no significant difference (P > 0.05) in THC and heavy metals in the body parts of crabs.  However, Zinc was highest in claw (993.4±91.3 mg/l) and body tissues (32.5±1.9 mg/l), Pb was highest in carapace (34.6±2.8 mg/l) and gill (151.9±21.6 mg/l) while THC was highest in intestine (39.5±2.9 mg/l) and gut (52.4±13.4 mg/l). The order of concentration is Zn>Pb>THC>Cd. Male crabs had slightly higher THC and heavy metal concentration than female crabs probably because of their large size. There is negative correlation between carapace area and THC concentration (R = -0.246), meaning THC decreases with increasing carapace size. Internal parts of crab had higher THC and heavy metal concentration than external parts. These results show that there is high bioaccumulation of THC and heavy metals in crab, which is above WHO/FAO standard. This implies that the crabs are unfit for human consumption. The smaller the crab the better it is for consumption in terms of bioaccumulation of pollutants.