Stream denitrification across biomes and its response to anthropogenic nitrate loading
Stream denitrification across biomes and its response to anthropogenic nitrate loading
Date
2007-06-06
Authors
Mulholland, Patrick J.
Helton, Ashley M.
Poole, Geoffrey C.
Hall, Robert O.
Hamilton, Stephen K.
Peterson, Bruce J.
Tank, Jennifer L.
Ashkenas, Linda R.
Cooper, Lee W.
Dahm, Clifford N.
Dodds, Walter K.
Findlay, Stuart E. G.
Gregory, Stanley V.
Grimm, Nancy B.
Johnson, Sherri L.
McDowell, William H.
Meyer, Judy L.
Valett, H. Maurice
Webster, Jackson R.
Arango, Clay P.
Beaulieu, Jake J.
Bernot, Melody J.
Burgin, Amy J.
Crenshaw, Chelsea L.
Johnson, Laura T.
Niederlehner, B. R.
O'Brien, Jonathan M.
Potter, Jody D.
Sheibley, Richard W.
Sobota, Daniel J.
Thomas, Suzanne M.
Helton, Ashley M.
Poole, Geoffrey C.
Hall, Robert O.
Hamilton, Stephen K.
Peterson, Bruce J.
Tank, Jennifer L.
Ashkenas, Linda R.
Cooper, Lee W.
Dahm, Clifford N.
Dodds, Walter K.
Findlay, Stuart E. G.
Gregory, Stanley V.
Grimm, Nancy B.
Johnson, Sherri L.
McDowell, William H.
Meyer, Judy L.
Valett, H. Maurice
Webster, Jackson R.
Arango, Clay P.
Beaulieu, Jake J.
Bernot, Melody J.
Burgin, Amy J.
Crenshaw, Chelsea L.
Johnson, Laura T.
Niederlehner, B. R.
O'Brien, Jonathan M.
Potter, Jody D.
Sheibley, Richard W.
Sobota, Daniel J.
Thomas, Suzanne M.
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Abstract
Worldwide, anthropogenic addition of bioavailable nitrogen (N) to the
biosphere is increasing and terrestrial ecosystems are becoming increasingly N
saturated, causing more bioavailable N to enter groundwater and surface waters.
Large-scale N budgets show that an average of about 20-25% of the N added to the
biosphere is exported from rivers to the ocean or inland basins, indicating
substantial sinks for N must exist in the landscape. Streams and rivers may be
important sinks for bioavailable N owing to their hydrologic connections with
terrestrial systems, high rates of biological activity, and streambed sediment
environments that favor microbial denitrification. Here, using data from 15N
tracer experiments replicated across 72 streams and 8 regions representing several
biomes, we show that total biotic uptake and denitrification of nitrate increase with
stream nitrate concentration, but that the efficiency of biotic uptake and
denitrification declines as concentration increases, reducing the proportion of instream
nitrate that is removed from transport. Total uptake of nitrate was related
to ecosystem photosynthesis and denitrification was related to ecosystem
respiration. Additionally, we use a stream network model to demonstrate that
excess nitrate in streams elicits a disproportionate increase in the fraction of nitrate
that is exported to receiving waters and reduces the relative role of small versus
large streams as nitrate sinks.
Description
Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 452 (2008): 202-205, doi:10.1038/nature06686.