Sarah E. Janssen Brett A. Poulin William P. Johnson Michael Tate Pieter Glatzel Tylor Rosera Grace Jane Armstrong Alain Manceau Samuel Francisco Lopez 2026 <p><span>Great Salt Lake (GSL) waterfowl have elevated mercury (Hg) concentrations, and&nbsp;</span><i>in vivo</i><span>&nbsp;detoxification of neurotoxic and bioaccumulative methylmercury (MeHg) can occur through Hg-selenium (Se) complexation, influencing the suitability of Hg consumption advisories. Here, we present Hg chemical speciation and Hg stable isotope measurements of brain, breast muscle, liver, and kidney samples from two GSL duck species─northern shoveler (</span><i>Spatula clypeata</i><span>) and cinnamon teal (Spatula cyanoptera). Chemical and stable isotope measurements, along with high energy resolution fluorescence detected X-ray absorption near-edge structure (HERFD-XANES) spectroscopy, indicate the occurrence of&nbsp;</span><i>in vivo</i><span>&nbsp;MeHg demethylation in both bird species. The percentage of total Hg (THg) as MeHg (% MeHg) varied with tissue type (brain &gt; breast muscle &gt; kidney &gt; liver), and differences between δ</span>²⁰²<span>&nbsp;THg and δ</span>²⁰²<span>&nbsp;MeHg were linearly correlated with % MeHg. Demethylated inorganic Hg was a mixture of Hg-dithiolate (Hg(SR)</span>₂<span>) and Hg-tetraselenolate (Hg(Sec)</span>₄<span>) in both bird species. Notably, liver THg concentrations were elevated in northern shoveler liver tissues relative to those of cinnamon teal (7.54 ± 4.69 mg/kg versus 2.19 ± 1.27 mg/kg, dry weight, respectively) and % MeHg liver values were significantly lower (40% ± 19% versus 68% ± 14%), indicating taxonomic differences in Hg detoxification and depuration. THg concentrations in waterfowl species from this study were comparable to previously reported levels, indicating that elevated Hg concentrations in northern shoveler and cinnamon teal at GSL have persisted over the past two decades. Due to&nbsp;</span><i>in vivo</i><span>&nbsp;demethylation, we show that THg is not an effective proxy for MeHg within duck species, carrying implications for current GSL waterfowl consumption advisories and assessments exposure risk. This study highlights important differences in MeHg detoxification between waterbird taxa and provides further insights into Hg toxicity risk to GSL waterbirds.</span></p> application/pdf 10.1021/envhealth.6c00108 en ACS Publications Comparing in vivo methylmercury detoxification in hunted duck: Implications for wildlife and human health article