Evaluation of Metallothioneins in Blue Mussels (Mytilus galloprovincialis) as a Biomarker of Mercury and Cadmium Exposure in the Slovenian waters (Gulf of Trieste): A Long-term Field Study

High anthropogenic pressures (pollution, exploration of natural resources, building, etc.) in the marine environment demand human monitoring. In recent decades European environmental monitoring programs have become more and more sophisticated and comprehensive, culminating with the Water Framework Directive (WFD, 2000/60/EC9) In order to assess the spatial distribution and temporal trends of pollution with metals in the coastal sea of Slovenia, the level of metallothioneins (MT) was determined in blue mussels from three sampling locations, twice per year for a period of 10 years. MT concentrations ranged from 45 to 163 μg g-1 w.w. in March, and from 46 to 144 μg g-1 w.w. in the September sampling. The metals content was determined in whole mussel tissue once per year at two stations. The cadmium (Cd) concentration was in the range from 0.50 to 1.11 mg kg-1, while the concentration of mercury (Hg) was in the range from 0.70 to 0.237 mg kg-1. Results revealed no significant seasonal differences or differences between sampling sites in MT content, as well as variations in the content of Cd and Hg in mussels’ tissue during the examined period. The MT and metal content in mussels are not well correlated and other factors may have caused the fluctuations observed in MT content between years. This supports the notion that biomonitoring data have to be interpreted cautiously, taking into account various other factors that may influence MT induction.