title: Mercury stable isotopes in seabird eggs reflect a gradient from terrestrial geogenic to oceanic mercury reservoirs.
abstract: Elevated mercury concentrations ([Hg]) were found in Alaskan murre (Uria spp.) eggs from the coastal embayment of Norton Sound relative to insular colonies in the northern Bering Sea-Bering Strait region. Stable isotopes of Hg, carbon, and nitrogen were measured in the eggs to investigate the source of this enrichment. Lower δ(13)C values in Norton Sound eggs (-23.3‰ to -20.0‰) relative to eggs from more oceanic colonies (-20.9‰ to -18.7‰) indicated that a significant terrestrial carbon source was associated with the elevated [Hg] in Norton Sound, implicating the Yukon River and smaller Seward Peninsula watersheds as the likely Hg source. The increasing [Hg] gradient extending inshore was accompanied by strong decreasing gradients of δ(202)Hg and Δ(199)Hg in eggs, indicating lower degrees of mass-dependent (MDF) and mass-independent Hg fractionation (MIF) (respectively) in the Norton Sound food web. Negative or zero MDF and MIF signatures are typical of geological Hg sources, which suggests murres in Norton Sound integrated Hg from a more recent geological origin that has experienced a relatively limited extent of aquatic fractionation relative to more oceanic colonies. The association of low δ(202)Hg and Δ(199)Hg with elevated [Hg] and terrestrial δ(13)C values suggested that Hg stable isotopes in murre eggs effectively differentiated terrestrial/geogenic Hg sources from oceanic reservoirs.
authors.affiliation: National Institute of Standards and Technology, Analytical Chemistry Division, Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, South Carolina 29412, United States. russell.day@nist.gov
authors.forename: Rusty D
authors.initials: RD
authors.lastname: Day
authors.forename: David G
authors.initials: DG
authors.lastname: Roseneau
authors.forename: Sylvain
authors.initials: S
authors.lastname: Berail
authors.forename: Keith A
authors.initials: KA
authors.lastname: Hobson
authors.forename: Olivier F X
authors.initials: OF
authors.lastname: Donard
authors.forename: Stacy S
authors.initials: SS
authors.lastname: Vander Pol
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Pugh
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Moors
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Long
authors.forename: Paul R
authors.initials: PR
authors.lastname: Becker
mesh_terms: D000818:Animals; D046091:Charadriiformes / Q000378:metabolism*; D005591:Chemical Fractionation; D017753:Ecosystem; D004784:Environmental Monitoring; D007553:Isotope Labeling; D008628:Mercury / Q000032:analysis*; D008629:Mercury Isotopes; D009792:Oceans and Seas; D010063:Ovum / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D008629:Mercury Isotopes; D014874:Water Pollutants, Chemical; D008628:Mercury