Heavy metal levels in the sediments of four Dar es Salaam mangroves. Accumulation in, and effect on the morphology of the periwinkle, Littoraria scabra (Mollusca: Gastropoda).

Heavy metals were determined in the soft tissue and shells of the littorinid, Littoraria scabra, and in the sediments of four mangrove areas along the Dar es Salaam coastline where L. scabra was collected. Several metals accumulate, preferentially in the animals' soft body parts, but do not seem to affect the shell morphology of this species. Sediment-metal levels, measured in the direct vicinity of Dar es Salaam have increased dramatically over the last decade. Nonetheless, these levels are still lower compared to metal-sediment levels reported in polluted European and American estuaries. Soft-tissue metal levels detected in L. scabra are, nevertheless, with the exception of Cr and Zn, comparable to metal levels reported in other gastropod species.