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Recent ecological and biogeochemical changes in alpine lakes of Rocky Mountain National Park (Colorado, USA): A response to anthropogenic nitrogen deposition

Geobiology

By:
, , and ORCID iD
https://doi.org/10.1046/j.1472-4669.2003.00012.x

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Abstract

Dated sediment cores from five alpine lakes (>3200 m asl) in Rocky Mountain National Park (Colorado Front Range, USA) record near-synchronous stratigraphic changes that are believed to reflect ecological and biogeochemical responses to enhanced nitrogen deposition from anthropogenic sources. Changes in sediment proxies include progressive increases in the frequencies of mesotrophic planktonic diatom taxa and diatom concentrations, coupled with depletions of sediment δ15N and C : N values. These trends are especially pronounced since approximately 1950. The most conspicuous diatoms to expand in recent decades are Asterionella formosa and Fragilaria crotonensis. Down-core species changes are corroborated by a year-long sediment trap experiment from one of the lakes, which reveals high frequencies of these two taxa during autumn and winter months, the interval of peak annual limnetic [NO3-]. Although all lakes record recent changes, the amplitude of stratigraphic shifts is greater in lakes east of the Continental Divide relative to those on the western slope, implying that most nitrogen enrichment originates from urban, industrial and agricultural sources east of the Rocky Mountains. Deviations from natural trajectories of lake ontogeny are illustrated by canonical correspondence analysis, which constrains the diatom record as a response to changes in nitrogen biogeochemistry. These results indicate that modest rates of anthropogenic nitrogen deposition are fully capable of inducing directional biological and biogeochemical shifts in relatively pristine ecosystems.

Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Recent ecological and biogeochemical changes in alpine lakes of Rocky Mountain National Park (Colorado, USA): A response to anthropogenic nitrogen deposition
Series title:
Geobiology
DOI:
10.1046/j.1472-4669.2003.00012.x
Volume:
1
Issue:
2
Year Published:
2003
Language:
English
Publisher:
Wiley
Contributing office(s):
Fort Collins Science Center
Description:
16 p.
First page:
153
Last page:
168
Country:
United States
State:
Colorado
Other Geospatial:
Rocky Mountain National Park