Nitrogen deposition to lakes in national parks of the western Great Lakes region: Isotopic signatures, watershed retention, and algal shifts

William O. Hobbs, Brenda Moraska Lafrancois, Robert Stottlemyer, David Toczydlowski, Daniel R. Engstrom, Mark B. Edlund, James E. Almendinger, Kristin E. Strock, David Vandermeulen, Joan E. Elias, Jasmine E. Saros

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

Atmospheric deposition is a primary source of reactive nitrogen (Nr) to undisturbed watersheds of the Great Lakes region of the U.S., raising concerns over whether enhanced delivery over recent decades has affected lake ecosystems. The National Atmospheric Deposition Program (NADP) has been measuring Nr deposition in this region for over 35 years. Here we explore the relationships among NADP-measured Nr deposition, nitrogen stable isotopes (δ15N) in lake sediments, and the response of algal communities in 28 lakes situated in national parks of the western Great Lakes region of the U.S. We find that 36% of the lakes preserve a sediment δ15N record that is statistically correlated with some form of Nr deposition (total dissolved inorganic N, nitrate, or ammonium). Furthermore, measured long-term (since 1982) nitrogen biogeochemistry and inferred critical nitrogen loads suggest that watershed nitrogen retention and climate strongly affect whether sediment δ15N is related to Nr deposition in lake sediment records. Measurements of algal change over the last ~ 150 years suggest that Nr deposition, in-lake nutrient cycling, and watershed inputs are important factors affecting diatom community composition, in addition to direct climatic effects on lake physical limnology. The findings suggest that bulk sediment δ15N does reflect Nr deposition in some instances. In addition, this study highlights the interactive effects of Nr deposition and climate variability.

Original languageEnglish (US)
Pages (from-to)514-533
Number of pages20
JournalGlobal Biogeochemical Cycles
Volume30
Issue number3
DOIs
StatePublished - Mar 1 2016
Externally publishedYes

Keywords

  • diatom
  • lake sediment
  • National Park
  • nitrogen deposition
  • nitrogen stable isotopes
  • western Great Lakes region

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