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Increasing stoichiometric imbalance in North America’s largest lake: Nitrification in Lake Superior

Sterner, Robert W., Anagnostou, Eleni, Brovold, Sandra, Bullerjahn, George S., Finlay, Jacques C., Kumar, Sanjeev, McKay, R. Michael L. and Sherrell, Robert M. (2007) Increasing stoichiometric imbalance in North America’s largest lake: Nitrification in Lake Superior Geophysical Research Letters, 34, L10406. (doi:10.1029/2006GL028861).

Record type: Article


Lake Superior has exhibited a continuous, century-long increase in nitrate whereas phosphate remains at very low levels. Increasing nitrate and low phosphate has led to a present-day severe stoichiometric imbalance; Lake Superior’s deepwater NO3 :PO43 molar ratio is 10,000, more than 600 times the mean requirement ratio for primary producers. We examine the rate of [NO3?] increase relative to budgets for NO3 and fixed N. Nitrate in Lake Superior has continued to rise since 1980, though possibly at a reduced rate. We constructed whole-lake NO3 and N budgets and found that NO3 must be generated in the lake at significant rates. Stable O isotope results indicate that most NO3 in the lake originated by in-lake oxidation. Nitrate in the lake is responding not just to NO3 loading but also to oxidation of reduced forms of nitrogen delivered to the lake. The increasing [NO3]:[PO43] stoichiometric imbalance in this large lake is largely determined by these in-situ processes.

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Published date: 2007
Organisations: Geochemistry


Local EPrints ID: 339953
ISSN: 0094-8276
PURE UUID: add4dc49-4606-4023-86cd-3f6864ad5660

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Date deposited: 06 Jun 2012 12:36
Last modified: 18 Jul 2017 05:51

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Author: Robert W. Sterner
Author: Eleni Anagnostou
Author: Sandra Brovold
Author: George S. Bullerjahn
Author: Jacques C. Finlay
Author: Sanjeev Kumar
Author: R. Michael L. McKay
Author: Robert M. Sherrell

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