title: Shallow methylmercury production in the marginal sea ice zone of the central Arctic Ocean.
abstract: Methylmercury (MeHg) is a neurotoxic compound that threatens wildlife and human health across the Arctic region. Though much is known about the source and dynamics of its inorganic mercury (Hg) precursor, the exact origin of the high MeHg concentrations in Arctic biota remains uncertain. Arctic coastal sediments, coastal marine waters and surface snow are known sites for MeHg production. Observations on marine Hg dynamics, however, have been restricted to the Canadian Archipelago and the Beaufort Sea (<79 °N). Here we present the first central Arctic Ocean (79-90 °N) profiles for total mercury (tHg) and MeHg. We find elevated tHg and MeHg concentrations in the marginal sea ice zone (81-85 °N). Similar to other open ocean basins, Arctic MeHg concentration maxima also occur in the pycnocline waters, but at much shallower depths (150-200 m). The shallow MeHg maxima just below the productive surface layer possibly result in enhanced biological uptake at the base of the Arctic marine food web and may explain the elevated MeHg concentrations in Arctic biota. We suggest that Arctic warming, through thinning sea ice, extension of the seasonal sea ice zone, intensified surface ocean stratification and shifts in plankton ecodynamics, will likely lead to higher marine MeHg production.
authors.affiliation: Geosciences Environment Toulouse (GET), Observatoire Midi-Pyrénées (OMP), UMR CNRS 5563, UMR IRD 234, 14 avenue Edouard Belin, Université Paul Sabatier, 31400 Toulouse, France.
authors.forename: Lars-Eric
authors.initials: LE
authors.lastname: Heimbürger
authors.affiliation: Geosciences Environment Toulouse (GET), Observatoire Midi-Pyrénées (OMP), UMR CNRS 5563, UMR IRD 234, 14 avenue Edouard Belin, Université Paul Sabatier, 31400 Toulouse, France.
authors.forename: Jeroen E
authors.initials: JE
authors.lastname: Sonke
authors.affiliation: ISTerre, Université Joseph Fourier, BP 53, 38041 Grenoble, France.
authors.forename: Daniel
authors.initials: D
authors.lastname: Cossa
authors.affiliation: Geosciences Environment Toulouse (GET), Observatoire Midi-Pyrénées (OMP), UMR CNRS 5563, UMR IRD 234, 14 avenue Edouard Belin, Université Paul Sabatier, 31400 Toulouse, France.
authors.forename: David
authors.initials: D
authors.lastname: Point
authors.affiliation: Geosciences Environment Toulouse (GET), Observatoire Midi-Pyrénées (OMP), UMR CNRS 5563, UMR IRD 234, 14 avenue Edouard Belin, Université Paul Sabatier, 31400 Toulouse, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Lagane
authors.affiliation: Geosciences Environment Toulouse (GET), Observatoire Midi-Pyrénées (OMP), UMR CNRS 5563, UMR IRD 234, 14 avenue Edouard Belin, Université Paul Sabatier, 31400 Toulouse, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Laffont
authors.affiliation: University of Miami Rosenstiel School of Marine &Atmospheric Science, Miami, Florida 33149 USA.
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Galfond
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany.
authors.forename: Marcel
authors.initials: M
authors.lastname: Nicolaus
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Rabe
authors.affiliation: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, 27570 Bremerhaven, Germany.
authors.forename: Michiel Rutgers
authors.initials: MR
authors.lastname: van der Loeff
mesh_terms: D001110:Arctic Regions; D058448:Biota; D004784:Environmental Monitoring; D046448:Ice Cover; D008628:Mercury / Q000032:analysis; D008767:Methylmercury Compounds / Q000032:analysis*; D009792:Oceans and Seas; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury