Mercury in the bivalve Anadara ( Senilia) senilis from Ghana and Nigeria

Samples of the bivalve Anadara ( Senilia) senilis collected from a closed lagoon (Sakumo) and two open lagoons in Ghana (Benya and Ningo; n=550), and the Bonny river estuary in Nigeria ( n=620), were analyzed for their total and organic mercury content. Total mercury concentration showed significant spatial differences, with median values of 0.1 μg/g dry wt. in the closed lagoon, 0.2 in the estuary and 0.3 in the open lagoons. Concentration tended to be higher during the dry season in the lagoons, but lower in the estuary. The median relative organic concentration varied between 20 and 60% methyl Hg, depending on location and season. Age effects were detected in the lagoons, total Hg concentration decreasing with length.