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The aim of this study was to determine the distribution of total mercury (THg), methylmercury (CH 3 Hg + ), and inorganic mercury (Hg inorg ) in the tissues and organs of fish depending on species, tissue, and organ, and their bioaccumulation in tissues and biomagnification throughout the trophic web. The study included four species of fish (herring, sprat, cod, and eel) from the southern Baltic Sea. The concentrations of the different forms of mercury were determined in tissues and internal organs. Intra-specific differences in levels of THg, CH 3 Hg + , and Hg inorg in the tissues and organs were determined. Muscle contained the highest proportions of THg and CH 3 Hg + in comparison to that in the internal organs. Differences in concentrations of THg, CH 3 Hg + , and Hg inorg in the tissues and organs of fish were related to their preferred prey. The bioaccumulation of CH 3 Hg+ in the tissues and organs of predatory fish at the highest trophic levels was greater than in the liver and digestive tract of fish species at lower trophic levels, in which Hg inorg predominated. The high concentrations of CH 3 Hg + in eel and cod and the low levels in herring and sprat were linked with their food and the transfer of this element among species. The results suggested that the type of food, feeding habits, and trophic position were important parameters that influenced the transfer and biomagnification of mercury in fish.

This study determined the concentrations of copper (Cu), zinc (Zn), cadmium (Cd), lead (Pb), mercury (Hg), and arsenic (As) in flounder from the southern Baltic for the 1996-2003 period. Analysis of more than 200 samples was used to determine the following: (1) concentrations of Hg and As in muscle tissue of flounder from different regions of the southern Baltic; (2) concentrations of Hg in the muscle tissue of flounder of different sizes; and (3) temporal trends in the concentrations of trace metals during the 1996-2003 period. A positive correlation between fish length and Hg concentration was noted. Further, the concentrations of Hg and As in flounder were correlated with sampling site. The most heavily polluted region of the Polish Baltic zone was the eastern region of the Baltic Sea. The temporal trend analyses showed significant downward trends in concentrations of Cd, Hg, and Pb in the flounder from the 1996-2003 period. Data suggest a decrease in the concentration of these elements in the environment of the Polish zone of the Baltic. It is noteworthy that no upward trends were noted in the concentrations of trace metals in the fish studied. If the flounder selected for the study are recognized as bioindicators of environmental pollution, then it is possible to conclude that the changes in trace metals concentrations in the Polish zone of the Baltic Sea are being reduced.

This study is based on raw data obtained from 1 225 samples of herring (Clupea harengus), sprat (Sprattus sprattus), and cod (Gadus morhua) collected in the 1994-2003 period from the Polish coastal zone of the Baltic Sea. This paper presents the results of investigations of the contents of Cu, Zn, Cd, Pb, Hg, and As in fish. The aim was to identify temporal trends in trace metal contamination and variations in the concentrations of Hg in the flesh of herring, sprat, and cod of different lengths. A positive correlation between fish length and Hg concentration was noted for cod, sprat, and herring. The temporal trend analyses of heavy metal concentrations in the fish in the 1994-2003 period indicated ten significant downward trends out of eighteen tests; these referred to concentrations of Cd, Hg, and Pb in all the species studied, and to As in sprat. Concentrations of Cu and Zn remained stable in all the species studied, as did As in herring and cod. No upward trends were detected in the concentration of trace metals in the fish studied. Smaller scale temporal variations in concentrations of some elements were also observed and were associated with natural events, such as increased river discharge resulting from floods. The most likely factors which contributed to the observed downward trends in heavy metals concentrations in fish could possibly stem from lesser quantities of Cd, Pb, and Hg being introduced to the Baltic Sea with the waters of rivers from Baltic countries, including Poland, and atmospheric depositions in the 1994-2003 period. Diminishing trends of concentrations of these elements in Baltic Sea waters are also evidence of this. These facts might indicate that advantageous changes are occurring in the concentrations of heavy metals in the southern Baltic environment.