Heavy Metals in the Burrowing Bivalve Scrobicularia Plana from the Tamar Estuary in Relation to Environmental Levels

Abstract

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.

Lead pollution and its sources along the Turkish coast of the Black Sea

“…In the present study, the increase observed in the average lead concentrations in October and December coincided with an increase in the weight: size ratio. A similar observation was recorded by BRYAN & UYSAL (1978) who found an increase in lead concentration with increasing dry weight of whole soft body parts of the bivalve, Scrobicularia plana, from the Tamar Estuary in England. PHILLIPS (1978) reported concentrations of lead in mussels to be highest in mussels taken from low-salinity waters on the Scandinavian coasts.…”

Seasonal Variation and Inherent Variability of Trace Elements in Oysters and Their lmplications for Indicator Studies

“…For example, metals may vary in both concentration and total body load in bivalves with age or size (Boyden, 1974(Boyden, , 1977Bryan and Uysal, 1978). Season may also be a significant perturbant of element levels (Bryan, 1973;Frazier, 1975Frazier, , 1976Phillips, 1976a).…”

The role of sediments in the chemistry of aquatic systems - Proceedings of the sediment chemistry workshop, February 8-12, 1982

“…1978). Such correlations are most common in metalenriched environments (Boyden, 197'7;Bryan and Uysal, 1978;Strong and Luoma, 1 981) and appear to reflect lifelong, net metal accumulation (Cross and others, 1973). Recent studies point to mechanisms that might explain how lifelong metal accumulation could occur in enriclJ.ed environments coincident with metal fluxes that should eventually lead to a steady-state concentration.…”

“…Only animals exposed to methylmercury in food showed distributions similar to those observed in fish from nature, leading to the conclusion that food was the source of the metal. Bryan and Uysal (1978) concluded from tissue distributions that Cd, Co, Pb, and Zn, but possibly not Ag and Cu, in the burrowing clam Scrobicularia plana originated largely from food.…”