Mussels as biomonitors of point and diffuse sources of trace metals in theClyde Sea Area, Scotland

Following a series of international conferences on pollution of the North S ea, the UK Government committed itself in 1990 to reducing the inputs of ce rtain 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 Are a 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 observe d in metals loadings from point sources or in mussel body burdens. The exce ptions were cadmium, which showed downward trends with time in loadings and in concentrations in Clyde Estuary mussels, and lead, which showed a downw ard 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 sev erely affected by point source inputs, others by bulk contamination from fa r-field point sources, and others by diffuse sources of metals. (C) 1999 Pu blished by Elsevier Science Ltd on behalf of the IAWQ. All rights reserved.