Toxic metals (Cd, Pb) in flatfish, mollusc Macoma balthica, water and sediments from the southern Baltic Sea

Environmental pollution is a worldwide problem, with toxic metals being among the most noxious pollutants. Aquatic organisms can accumulate toxic elements from their environment through different pathways, including water, diet and sediments. The aim of the study was to determine the distribution of toxic metals (Cd and Pb) in tissues of three species of flatfish (Platichthys flesus, Pleuronectes platessa, Scophthalmus maximus), and in their environment (water, sediment and their prey mollusc Macoma balthica) in four regions of the southern Baltic Sea, in order to identify the most important pathways of metal uptake in these fish. The concentrations of toxic metal were measured in a graphite furnace by atomic absorption spectrometry. Toxic metal concentrations in flatfish liver were significantly higher than in the muscle tissue. The liver was the target organ for Cd and Pb accumulation. The flatfish liver, M. balthica, sediment, and water from the Gulf of Gdansk contained higher level of Pb than did the samples from the central Baltic Sea coast. The Pb concentrations in the liver of P. flesus and P. platessa showed positive correlations with Pb in the soft tissue of M. balthica, sediment and sea water. The high correlation coefficient values for Pb suggest that flatfish took up this metal through the food chain from molluscs. In turn, M. balthica took up Pb and Cd from sediment and water, which was confirmed by the high correlation coefficients for these metals between this mollusc and sediment and water. The positive correlations for concentrations Pb and Cd in sediment and in water indicate the next stage of the pathway along which the metals travel in the Baltic Sea environment.