TY - JOUR
T1 - Increasing stoichiometric imbalance in North America's largest lake
T2 - Nitrification in Lake Superior
AU - Sterner, Robert W.
AU - Anagnostou, Eleni
AU - Brovold, Sandra
AU - Bullerjahn, George S.
AU - Finlay, Jacques C.
AU - Kumar, Sanjeev
AU - McKay, Michael L.
AU - Sherrell, Robert M.
PY - 2007/5/28
Y1 - 2007/5/28
N2 - 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-]: [PO4 3-] stoichiometric imbalance in this large lake is largely determined by these in-situ processes.
AB - 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-]: [PO4 3-] stoichiometric imbalance in this large lake is largely determined by these in-situ processes.
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U2 - 10.1029/2006GL028861
DO - 10.1029/2006GL028861
M3 - Article
AN - SCOPUS:34447566116
SN - 0094-8276
VL - 34
JO - Geophysical Research Letters
JF - Geophysical Research Letters
IS - 10
M1 - L10406
ER -