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 littorini d, Littoraria scabra, and in the sediments of four mangrove areas along the Dar es Salaam coastline where L. scabra was collected. Several metals accu mulate, preferentially in the animals' soft body parts, but do not seem to affect the shell morphology of this species. Sediment-metal levels, measure d in the direct vicinity of Dar es Salaam have increased dramatically over the last decade. Nonetheless, these levels are still lower compared to meta l-sediment levels reported in polluted European and American estuaries. Sof t-tissue metal levels detected in L. scabra are, nevertheless, with the exc eption of Cr and Zn, comparable to metal levels reported in other gastropod species. (C) 2001 Elsevier Science Ltd. All rights reserved.