Abstract

A comparative survey of the levels of contamination of the two gastropods, of the Potomidae family, has been done in the lagoon Ebrié close to the city of Abidjan. It revealed that Tympanotonus fuscatus radula (TFR), adapt better to the conditions of the lagoon environment than Tympanotonus fuscatus fuscatus (TFF). Besides,T. fuscatus radula shows a higher bioaccumulation capacity of the trace elements than T. fuscatus fuscatus: the ratios of contamination index of T. fuscatus radula to those of T. fuscatus fuscatus are in the order of 1.5 for copper (Cu), 4.9 for iron (Fe), 3.2 for zinc (Zn), 95.9 for lead (Pb) and 6.7 for cadmium (Cd). Therefore T. fuscatus radula could be a better metallic pollution indicator than T. fuscatus fuscatus. A hierarchical classification analysis permitted, on the basis of trace elements contents in the soft tissues of T. fuscatus radula higher than 10%, to determine the polymetallic character of the pollution in the different sampling stations (with the exception of Biét 3) as well as the differences in the bioavailability of the trace elements. Besides, possible health risks linked to the consumption ofT. fuscatus radula exist because of the lead concentrations which, in 35.57% of the samples, are higher than the consumption standards of the European Union (EU) and the World Health Organisation (WHO). Even if the contents in cadmium are lower than the consumption standards of the EU and the WHO, the health risks linked to this trace element still remains because of its cumulative character in some vital organs of human. 

Key words: Trace element, gastropod, Tympanotonus fuscatus, bioaccumulation, Ebrié lagoon, Côte d’Ivoire.