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| Titel |
Biogeochemical response of alpine lakes to a recent increase in dust deposition in the Southwestern, US |
| VerfasserIn |
A. P. Ballantyne, J. Brahney, D. Fernandez, C. L. Lawrence, J. Saros, J. C. Neff |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 8, no. 9 ; Nr. 8, no. 9 (2011-09-23), S.2689-2706 |
| Datensatznummer |
250006129
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| Publikation (Nr.) |
 copernicus.org/bg-8-2689-2011.pdf |
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| Zusammenfassung |
| The deposition of dust has recently increased significantly over some
regions of the western US. Here we explore how changes in dust deposition
have affected the biogeochemistry of two alpine watersheds in Colorado, US.
We first reconstruct recent changes in the mass accumulation rate of
sediments and then we use isotopic measurements in conjunction with a
Bayesian mixing model to infer that approximately 95% of the inorganic
fraction of lake sediments is derived from dust. Elemental analyses of
modern dust indicate that dust is enriched in Ca, Cr, Cu, Mg, Ni, and in one
watershed, Fe and P relative to bedrock. The increase in dust deposition
combined with its enrichment in certain elements has altered the
biogeochemisty of these systems. Both lakes showed an increase in primary
productivity as evidenced by a decrease in carbon isotopic discrimination;
however, the cause of increased primary productivity varies due to
differences in watershed characteristic. The lake in the larger watershed
experienced greater atmospheric N loading and less P loading from the
bedrock leading to a greater N:P flux ratio. In contrast, the lake in the
smaller watershed experienced less atmospheric N loading and greater P
loading from the bedrock, leading to a reduced N:P flux ratio. As a result,
primary productivity was more constrained by N availability in the smaller
watershed. N-limited primary productivity in the smaller watershed was
partly ameliorated by an increase in nitrogen fixation as indicated by
reduced nitrogen isotopic values in more contemporary sediments. This study
illustrates that alpine watersheds are excellent integrators of changes in
atmospheric deposition, but that the biogeochemical response of these
watersheds may be mediated by their physical (i.e. watershed area) and
chemical (i.e. underlying geology) properties. |
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