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

Samples of the bivalve Anadara (Senilia) senilis collected from a closed la goon (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 tota l and organic mercury content. Total mercury concentration showed significa nt spatial differences, with median values of 0.1 mu g/g dry wt, in the clo sed lagoon, 0.2 in the estuary and 0.3 in the open lagoons. Concentration t ended to be higher during the dry season in the lagoons, but lower in the e stuary. 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. (C) 1998 Elsevi er Science B.V. All rights reserved.