Total and organic mercury in the Black Sea harbour porpoise Phocoena phocoena relicta

This paper reports on mercury (Hg) concentrations in different tissues (liv er, muscle, kidney, blubber and brain) of harbour porpoises Phocoena phocoe na found dead in the Black Sea between 1997 and 1999, mainly bycaught in fi shing nets (n = 79). Total Hg and organic Hg (MeHg) were determined. The ma in factor affecting Hg accumulation was, as expected, age, with MeHg concen tration increasing with age. Accumulation of high concentrations of inorgan ic Hg in the liver was probably due to a slow demethylation process implyin g the formation of tiemannite (HgSe). In older adults, liver concentrations reached 35 mug g(-1) dry weight ('ppm') total Hg and 3 mug g(-1) dw MeHg. A geographical comparison with existing data from other regions showed a ge nerally low Hg contamination of Black Sea porpoises, one order of magnitude lower than, e.g. in the North Sea. (C) 2001 Elsevier Science Ltd. All righ ts reserved.