The bioaccumulation of metals was investigated by analysis of liver, kidney, muscle and brain tissue of a pod of 21 long-finned pilot whales (Globicephala melas) of all ages stranded in Scotland, UK. The results are the first to report cadmium (Cd) passage through the blood-brain barrier of pilot whales and provide a comprehensive study of the long-term (up to 35years) mammalian exposure to the environmental pollutants. Additionally, linear accumulation of mercury (Hg) was observed in all studied tissues, whereas for Cd this was only observed in the liver. Total Hg concentration above the upper neurochemical threshold was found in the sub-adult and adult brains and methylmercury (MeHg) of 2.2mg/kg was found in the brain of one individual. Inter-elemental analysis showed significant positive correlations of Hg with selenium (Se) and Cd with Se in all studied tissues. Furthermore, differences in the elemental concentrations in the liver and brain tissues were found between juvenile, sub-adult and adult groups. The highest concentrations of manganese, iron, zinc, Se, Hg and MeHg were noted in the livers, whereas Cd predominantly accumulated in the kidneys. High concentrations of Hg and Cd in the tissues of pilot whales presented in this study reflect ever increasing toxic stress on marine mammals.
M. M. Lawan for his helpful discussions about Se and advice on ICP-MS. C. C. Brombach for his introduction to CV-AFS and to D. Bellis for valuable comments and reviewing the English language in the manuscript. ZG would also like to thank the College of Physical Sciences at the University of Aberdeen and Chevron USA for the provided studentship. FLR and AB acknowledge Scottish Marine Animal Stranding Scheme and Marine Scotland for the funding.
- marine mammals
- trace elements
- blood–brain barrier