title: A coherent signature of anthropogenic nitrogen deposition to remote watersheds of the Northern Hemisphere.
abstract: Humans have more than doubled the amount of reactive nitrogen (Nr) added to the biosphere, yet most of what is known about its accumulation and ecological effects is derived from studies of heavily populated regions. Nitrogen (N) stable isotope ratios ((15)N:(14)N) in dated sediments from 25 remote Northern Hemisphere lakes show a coherent signal of an isotopically distinct source of N to ecosystems beginning in 1895 ± 10 years (±1 standard deviation). Initial shifts in N isotope composition recorded in lake sediments coincide with anthropogenic CO(2) emissions but accelerate with widespread industrial Nr production during the past half century. Although current atmospheric Nr deposition rates in remote regions are relatively low, anthropogenic N has probably influenced watershed N budgets across the Northern Hemisphere for over a century.
authors.affiliation: School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA. gholt@uw.edu
authors.forename: Gordon W
authors.initials: GW
authors.lastname: Holtgrieve
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Schindler
authors.forename: William O
authors.initials: WO
authors.lastname: Hobbs
authors.forename: Peter R
authors.initials: PR
authors.lastname: Leavitt
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Ward
authors.forename: Lynda
authors.initials: L
authors.lastname: Bunting
authors.forename: Guangjie
authors.initials: G
authors.lastname: Chen
authors.forename: Bruce P
authors.initials: BP
authors.lastname: Finney
authors.forename: Irene
authors.initials: I
authors.lastname: Gregory-Eaves
authors.forename: Sofia
authors.initials: S
authors.lastname: Holmgren
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Lisac
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Lisi
authors.forename: Koren
authors.initials: K
authors.lastname: Nydick
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Rogers
authors.forename: Jasmine E
authors.initials: JE
authors.lastname: Saros
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Selbie
authors.forename: Mark D
authors.initials: MD
authors.lastname: Shapley
authors.forename: Patrick B
authors.initials: PB
authors.lastname: Walsh
authors.forename: Alexander P
authors.initials: AP
authors.lastname: Wolfe