Nitrate uptake across biomes and the influence of elemental stoichiometry: A new look at LINX II

Considering recent increases in anthropogenic N loading, it is essential to identify the controls on N removal and retention in aquatic ecosystems because the fate of N has consequences for water quality in streams and downstream ecosystems. Biological uptake of nitrate (NO3−) is a major pathway by...

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Bibliographic Details
Published in:Global biogeochemical cycles 2016-08, Vol.30 (8), p.1183-1191
Main Authors: Wymore, Adam S., Coble, Ashley A., Rodríguez‐Cardona, Bianca, McDowell, William H.
Format: Article
Language:English
Subjects:
Biogeochemistry
Ecosystems
elemental ratios
Freshwater
LINX II
nitrate
Nitrates
nutrient additions
stream ecosystems
Velocity
Watersheds
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Summary:Considering recent increases in anthropogenic N loading, it is essential to identify the controls on N removal and retention in aquatic ecosystems because the fate of N has consequences for water quality in streams and downstream ecosystems. Biological uptake of nitrate (NO3−) is a major pathway by which N is removed from these ecosystems. Here we used data from the second Lotic Intersite Nitrogen eXperiment (LINX II) in a multivariate analysis to identify the primary drivers of variation in NO3− uptake velocity among biomes. Across 69 study watersheds in North America, dissolved organic carbon:NO3− ratios and photosynthetically active radiation were identified as the two most important predictor variables in explaining NO3− uptake velocity. However, within a specific biome the predictor variables of NO3− uptake velocity varied and included various physical, chemical, and biological attributes. Our analysis demonstrates the broad control of elemental stoichiometry on NO3− uptake velocity as well as the importance of biome‐specific predictors. Understanding this spatial variation has important implications for biome‐specific watershed management and the downstream export of NO3−, as well as for development of spatially explicit global models that describe N dynamics in streams and rivers. Key Points Across biomes NO3− uptake is best predicted by DOC:NO3− ratios and photosynthetically active radiation No universal driver of NO3− uptake was identified Controls on NO3− uptake vary by biome
ISSN:0886-6236
1944-9224
DOI:10.1002/2016GB005468