Quantifying the production of dissolved organic nitrogen in headwater streams using 15N tracer additions

View/ Open
Date
2013-07Author
Johnson, Laura T.
Concept link
Tank, Jennifer L.
Concept link
Hall, Robert O.
Concept link
Mulholland, Patrick J.
Concept link
Hamilton, Stephen K.
Concept link
Valett, H. Maurice
Concept link
Webster, Jackson R.
Concept link
Bernot, Melody J.
Concept link
McDowell, William H.
Concept link
Peterson, Bruce J.
Concept link
Thomas, Suzanne M.
Concept link
Metadata
Show full item recordCitable URI
https://hdl.handle.net/1912/6552As published
https://doi.org/10.4319/lo.2013.58.4.1271DOI
10.4319/lo.2013.58.4.1271Abstract
Most nitrogen (N) assimilation in lake and marine ecosystems is often subsequently released via autochthonous dissolved organic nitrogen (DON) production, but autochthonous DON production has yet to be quantified in flowing waters. We measured in-stream DON production following 24 h 15N-nitrate () tracer additions in 36 headwater streams, a subset of sites from the second Lotic Intersite Nitrogen eXperiment. Streams were located in five North American ecoregions and drained basins dominated by native vegetation, agriculture, or urban land use. Using a two-compartment model, we could quantify DON production in 15 streams as a function of DO15N derived from 15N tracer in biomass compartments. The streams with detectable DON production had higher % modified land use (agriculture + urban) in their basins than did streams with undetectable DON production. Median DON production represented 8% of total uptake when we used N biomass estimates based on N assimilated over 1 d (measured directly from the 15N additions). Median DON production was 17% of total uptake when we used N assimilated over 42 d (extrapolated from previous 15N tracer studies). Variation in DON production was positively correlated with ecosystem respiration, indicating that stream heterotrophy may influence DON production. In-stream DON production was similar in magnitude to stream denitrification and nitrification, indicating that the production of autochthonous DON can represent a substantial transformation of stream N. Our results confirm that headwater streams can quickly convert inorganic N into organic forms, although the ultimate fate of DON remains unclear.
Description
Author Posting. © Association for the Sciences of Limnology and Oceanography, 2013. This article is posted here by permission of Association for the Sciences of Limnology and Oceanography for personal use, not for redistribution. The definitive version was published in Limnology and Oceanography 58 (2013): 1271-1285, doi:10.4319/lo.2013.58.4.1271.