Abstract. Levels of heavy metal (cadmium, zinc, copper, lead, nickel, iron) concentrations in tissues of snails and mollusks collected from the Varna Gulf, Black Sea were determined using atomic absorption spectroscopy. In principle, no elevated concentrations of toxic metals were detected as compared to the critical values offered by the environmental agency in Bulgaria. Nevertheless, the monitoring results offer an opportunity to assess in a reliable way the sea water quality using the marine organisms as biomonitors. The cluster analysis applied revealed that the accumulation of heavy metals indicated clustering into several groups, where the metals found in the shell were significantly different from the other soft tissues. The multivariate analysis indicates the ability of snails and mollusks to accumulate heavy metals, hence fulfilling the criteria as good biomonitors.

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