Heavy metals in the burrowing bivalve scrobicularia plana from the tamar estuary in relation to environmental levels

Concentrations of ten metals (Ag, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) have been measured in the whole soft parts and digestive gland of the burrowing bivalve Scrobicularia plana (da Costa) over its range of distribution in the Tamar estuary. Four metals (Cu, Fe, Mn, Zn) have been analysed in the individual tissues including the shell. As far as possible, concentrations in the animals have been related to those in the environment. Seasonal variation, level on the shore and size of animal have also been considered. Partitioning of metals between the digestive gland and remaining soft tissues suggests that uptake of Cd, Co, Cr, Ni, Pb and Zn occurs mainly through ingestion of sediments. Generally, more than 75 % of these metals was found in the digestive gland. This organ contributed less to the total amount of Cu and Ag (30-40 %), Mn (51-80 %) and Fe (3-20 %). Lower values of Mn and Fe were found upstream where the availability of'soluble’ metals to the animals was higher. Concentrations of Cd, Co, Cr, Ni, Pb and Zn in the whole soft parts increased markedly with size, whereas Fe remained relatively constant and levels of Ag, Cu and Mn decreased. In the shell, most of the Mn was incorporated in the matrix, presumably via the mantle, whereas appreciable amounts of Cu, Fe and Zn were probably incorporated directly from solution by adsorption. Scrobicularia appears to have potential as an indicator of the availability of metals in estuaries and results for Cu, Fe, Mn and Zn suggest that there were no important changes in the Tamar estuary between 1969 and 1974. © 1978, Marine Biological Association of the United Kingdom. All rights reserved.Department of the Environment, Australian Government: DGR 480/51We are very grateful to U.N.E.S.C.O. for a grant to one of us (H.U.) and to the then Director Dr J. E. Smith for providing facilities. Thanks are also due to Mr L. G. Hummerstone for his assistance throughout this work and to the South West Water Authority for providing flow data for the River Tamar. Part of the research was financed by the Department of the Environment under Contract DGR 480/51. -