Distribution of organic and inorganic mercury in the tissues and organs of fish from the southern Baltic Sea.

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.