Metal pollution as health indicator of lake ecosystems.

As part of a long-term monitoring study of the anthropogenic pollution of the Lake of Balaton (Hungary) the concentrations of toxic metals (Cd2+, Hg2+, Pb2+), as well as of bioelements (Cu2+ and Zn2+) were measured in the muscle, gill and liver of bream (Abramis brama L.) collected in the open water during the autumn of 1999, The highest Cd, Cu, Pb and Zn concentrations were detected in the gill and liver of fish, whereas the highest Hg concentrations were measured in the muscle. The maximum metal concentrations measured in the muscle of bream were generally below maximum permissible levels for human consumption established by the Hungarian Food Directorate. Depending on the sampling site, significantly higher Cd, Hg and Pb concentrations (p < 0.05) were detected in the muscle of fish samples collected from the Western basin, while no significant differences were observed for Cu and Zn. In the muscle and gill an increasing trend of heavy metal (Cd and Cu) load characterizes the individuals of the 2-4 calendar age group (p < 0.05), while for the older specimens the concentration of these elements decreased significantly (p < 0.05). Positive relationships on the whole age scale were found for Cd in the liver, for Pb in the gill, and for Hg both in the muscle and the liver of fish.