Article

Water, Air, & Soil Pollution

, Volume 216, Issue 1, pp 193-202

Critical Nitrogen Deposition Loads in High-elevation Lakes of the Western US Inferred from Paleolimnological Records

  • Jasmine E. SarosAffiliated withClimate Change Institute, and School of Biology and Ecology, University of Maine Email author 
  • , David W. ClowAffiliated withUS Geological Survey, Water Resources Discipline
  • , Tamara BlettAffiliated withNational Park Service, Air Resources Division
  • , Alexander P. WolfeAffiliated withDepartment of Earth and Atmospheric Sciences, University of Alberta

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Abstract

Critical loads of nitrogen (N) from atmospheric deposition were determined for alpine lake ecosystems in the western US using fossil diatom assemblages in lake sediment cores. Changes in diatom species over the last century were indicative of N enrichment in two areas, the eastern Sierra Nevada, starting between 1960 and 1965, and the Greater Yellowstone Ecosystem, starting in 1980. In contrast, no changes in diatom community structure were apparent in lakes of Glacier National Park. To determine critical N loads that elicited these community changes, we modeled wet nitrogen deposition rates for the period in which diatom shifts first occurred in each area using deposition data spanning from 1980 to 2007. We determined a critical load of 1.4 kg N ha−1 year−1 wet N deposition to elicit key nutrient enrichment effects on diatom communities in both the eastern Sierra Nevada and the Greater Yellowstone Ecosystem.

Keywords

Critical load Atmospheric nitrogen deposition Alpine lake ecosystems Diatoms