Mussels as biomonitors of point and diffuse sources of trace metals in the clyde sea area, Scotland

Abstract

Following a series of international conferences on pollution of the North Sea, the UK Government committed itself in 1990 to reducing the inputs of certain dangerous substances reaching the aqueous environment from point and diffuse sources. The target was a 50% reduction in loadings over the period 1985-95. Metals loadings from rivers and sewage works to the Clyde Sea Area are presented for the period 1990-97. These are compared to trace metals body burdens in mussels collected from shores throughout the Clyde Sea Area over the period 1980-97. For most metals, no clear trend either increasing or decreasing was observed in metals loadings from point sources or in mussel body burdens. The exceptions were cadmium, which showed downward trends with time in loadings and in concentrations in Clyde Estuary mussels, and lead, which showed a downward trend in mussel concentrations. Metals loadings from point sources may have reached baseline levels, below which further reductions will be difficult to achieve. Elevated mussel body burdens of specific metals provided good evidence that some shores are severely affected by point source inputs, others by bulk contamination from far-field point sources, and others by diffuse sources of metals.