Mercury and selenium in the muscle of piscivorous common mergansers (Mergus merganser) from a selenium-deficient European country

• First study on Hg and Se in the muscle of ducks from a European Se-deficient area.
• Mercury forms (THg, MeHg, InHg) and selenium were assayed in duck muscles.
• In the muscle of merganser an unexpectedly high value of THg:Se molar ratio was revealed.
• Bioavailability of Se and Hg in Europe co-decide the Hg:Se ratio in the muscles of mergansers.

Although the relationship between mercury (Hg) and selenium (Se) has been studied in wild birds in areas with sufficient or excessive Se levels, little is known about this relationship in areas where the supply of Se is limited. As Hg detoxification is based on the production of biologically inactive Hg–Se complexes, the aim of this study was to investigate the relationships between the concentrations of total mercury (THg), methylmercury (MeHg), inorganic mercury (InHg=THg−MeHg), percent MeHg of THg, Se and molar ratios (THg:Se, MeHg:Se, InHg:Se) in the breast muscle (n=16) of the piscivorous common mergansers (Mergus merganser) from a Se-deficient and moderately Hg-polluted area in Poland. Mergansers were divided into two groups differing in condition (A—very good condition; C—moderate condition). Concentrations of THg, MeHg and Se were determined by atomic absorption spectrometry, modified gas chromatography atomic fluorescence spectroscopy, and spectrofluorometric methods, respectively. In all studied mergansers, mean concentrations of THg, MeHg, InHg, and Se in muscle were 2.63, 1.92, 0.46, and 0.54 µg g−1 dw, respectively. THg and MeHg concentrations in the muscle of group A mergansers were greater than in group C. The ratio of THg:Se was higher in group A than in group C (2.32 vs 1.36; p<0.01), as well as the molar ratio of MeHg:Se (A vs C: 1.98 vs 1.03; p<0.05). Comparisons between mergansers from Poland and Canada showed similar THg and percent MeHg in the muscle, but mergansers from Poland had several times lower Se levels and higher THg:Se ratios (>2.0) than the Canadian mergansers and other European and North American waterbirds. We found statistically significant positive correlations (MeHg–THg, percent MeHg/THg–MeHg, percent InHg/THg–InHg, THg:Se–THg, MeHg:Se–THg, THg:Se–MeHg, MeHg:Se–MeHg, InHg:Se–InHg, MeHg:Se–THg:Se) and some negative correlations (percent InHg/THg–MeHg, percent MeHg/THg–InHg, THg:Se–Se, MeHg:Se–Se). As THg and percent MeHg in the studied mergansers were similar to populations living in non-Se-deficient areas, it is likely that different mechanisms of muscle Hg detoxification have evolved in mergansers populations living in Se-deficient areas.

Relation between: A) concentrations of total mercury (THg) and methylmercury (MeHg); B) concentration of inorganic mercury (InHg) and percentage of MeHg in THg expressed as MeHg/THg (%); C) concentration THg and Hg:Se molar ratio (THg – THg:Se circles and continuous line; THg – MeHg:Se squares and dotted line; THg – InHg:Se triangles) in the muscle of common mergansers from Poland.Figure optionsDownload as PowerPoint slide