Seasonal variation in trace metal contents in oyster Crassostrea gasar from the Milliardaires Bay, Côte d’Ivoire

Abstract

To assess seasonal variations in trace metals contents in oyster Crassostrea gasar, samples were collected from six selected stations in Milliardaires Bay (Côte d’Ivoire) in the dry, flood and rainy seasons. Lead (Pb), cadmium (Cd), nickel (Ni), manganese (Mn) and zinc (Zn) concentrations were determined in the soft tissues by flame atomic absorption spectroscopy. Average (±standard deviation) concentrations of Pb, Cd, Ni, Mn, and Zn ranged from 40.06±124.77 to 301.91±216.27, 1.44±0.87 to 2.29±1.64, 23.86±18.46 to 172.32±518.55, 25.96±19.41 to 55.00±63.20 and 2537.34±1537.78 to 3322.99±2096.71 μg/g dry weight respectively. According to the two-way ANOVA analysis of variance, seasonal variations of Pb, Ni, and Zn were statistically significant (p 0.0001), at the opposite of Cd (p=0.9977) and Mn (p=0.7780) ones. Pb exhibited highest contents in the dry season, while those of Cd and Zn recorded in the flood and rainy ones. The seasonal variations of Ni and Zn were found dependent on the individual location each sampling station. The concentrations of the toxic metals (Pb and Cd) were of particular concern, calling efforts to address the contamination problem in Milliardaires Bay.