Animals that are higher on the trophic chain, such as waterbirds that primarily rely on fish, are at risk for ingesting methylmercury in their diet, which is then stored in their tissues and cycles through their organs.
Studying the isotopic fractionation of mercury in birds using stable mercury isotopes can answer critical questions about methylmercury detoxification. USGS and university researchers analyzed tissues and feathers from three deceased waterbirds—a Clark’s grebe, a Forster’s tern, and a south polar skua—quantifying differences in mercury concentrations between breast feathers, pectoral muscle, kidneys, liver, and the brain to determine how mercury cycles through the tissues. Chemical and isotope measurements for mercury and selenium were analyzed using a multi-collector inductively coupled plasma mass spectrometer and/or HR-XANES spectra. They found significant mercury toxicity in bird tissues and discovered that up to 86 percent of the methylmercury was demethylated to inorganic mercury species, primarily in the liver and kidneys. This study documents an emerging technique in toxicokinetic modeling of the transformation and redistribution of in vivo mercury.
Poulin, B.A., Janssen, S.E., Rosera, T.J., Krabbenhoft, D.P., Eagles-Smith, C.A., Ackerman, J.T., Stewart, A.R., Kim, E., Baumann, Z., Kim, J., Manceau, A., 2021, Isotope fractionation from in vivo methylmercury detoxification in waterbirds: ACS Earth and Space Chemistry, v. 5, no. 5, p. 990-997.
(Credit: Ken Phenicie. Photo courtesy of USFWS)