Trace metal concentrations in mussels: comparison between estuarine, coastal and offshore regions in the southeastern North Sea from 1983 to 1986

Abstract

The blue mussel Mytilus edulis was used for monitoring trace metal contamination in the southeastern North Sea. Metal concentrations in mussels from the estuaries of Ems, Jade and Elbe were compared with those from the inner German Bight, from a region off southern Jylland, and the open sea. In some cases, M. edulis from offshore areas contained metal concentrations as high as specimens from the estuaries. It is suggested that the unexpected high cadmium and lead levels in mussels from the central North Sea are due to (1) changes in trace metal speciation--an increasing bioavailability counteracts declining concentrations in seawater towards the open sea; (2) the pattern of residual currents--a great part of the pollutants brought into the sea around the British Isles settles and accumulates in the central North Sea; (3) oxygen deficiencies--in certain regions this leads to pronounced changes in redox conditions in sediments, thus allowing remobilisation.