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Influence of Nitrogen on Phytoplankton Biomass and Community Composition in Fifteen Snowy Range Lakes (Wyoming, U.S.A.)

Brenda Moraska Lafrancois, Koren R. Nydick and Bethany Caruso
Arctic, Antarctic, and Alpine Research
Vol. 35, No. 4 (Nov., 2003), pp. 499-508
Stable URL: http://www.jstor.org/stable/1552353
Page Count: 10
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Influence of Nitrogen on Phytoplankton Biomass and Community Composition in Fifteen Snowy Range Lakes (Wyoming, U.S.A.)
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Abstract

Nitrogen (N) deposition has been implicated in changes in surface water chemistry and algal composition in several dilute mountain lakes of the western United States. Lakes of the Snowy Range (Medicine Bow National Forest, Wyoming) appear to have low nitrate concentrations currently, and 2 Snowy Range lakes showed strong eutrophication responses to N or N + phosphorus (P) additions in previous enclosure experiments. In this study, we explored the regional extent of phytoplankton N limitation by examining a nutrient ratio index (dissolved inorganic nitrogen:total phosphorus) and phytoplankton species-environment relationships across 15 Snowy Range lakes. Based on this index, we estimate that phytoplankton biomass in the study lakes is largely N limited or N + P colimited. In addition, redundancy analysis demonstrated strong relationships between phytoplankton species composition and N gradients, with chrysophyte taxa favored in low-N lakes and cyanophytes and chlorophytes favored in higher-N lakes. We conclude that both phytoplankton biomass and community structure are sensitive indicators of N gradients in lakes of the Snowy Range, and that eutrophication responses to future increases in N loading could be widespread in these and other low-N lakes.

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