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

Abstract

The bivalve mollusc Scrobicularia plana (da Costa) is very common in the estuaries of South-West England and lives in permanent burrows in intertidal sediments ranging from soft mud to fairly hard sand and sometimes gravel. Although it obtains some of its food by filtering the overlying water, Scrobicularia is mainly a deposit feeder (Hughes, 1969). In addition to its widespread distribution, Scrobicularia has several features which make it attractive as a possible indicator organism for metallic contamination. It is more tolerant of low salinities than most common estuarine bivalves, usually penetrating farther upstream than Macoma balthica, Mytilus edulis and Cerastoderma edule (Percival, 1929; Spooner & Moore, 1940; Bryan & Hummerstone, 1977). Also, it lives for over ten years, usually attaining a length of 4–5 cm, and its rate of growth can be estimated from rings on the shell (Green, 1957; Hughes, 1970).