Integrated cellular stress indices in trace metal contamination: critical evaluation in a field study

Metal bound to metallothioneins and cytosolic proteins significantly increased in the digestive gland of mussels Mytilus edulis exposed in the GEEP Workshop mesocosm experiment to different levels of a copper and diesel oil mixture. Analysis performed on mussels sampled at 4 field sites in Langesundfjord, Noway, showed that the mussels were contaminated by metals, although to a limited degree. The concentration of metal bound to thioneins was essentially the same in the digestive gland extracts from mussels sampled at reference and polluted sites, but the values of copper bound to cytosolic proteins significantly increased at the field sites characterized by heavy metal pollution. These results indicate that the parameters studied (metals bound to cytosolic proteins and to metallothioneins) can be considered as satisfactory integrated stress indices in evaluating the biological impact of heavy metal contamination. Calcium concentration significantly increased in the digestive gland of mussels exposed to pollutants in the field as well as in the highest dosed mesocosm basins. The possibility of further application of this finding as a general stress index is discussed.