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Long-term fertilization alters the relative importance of nitrate reduction pathways in salt marsh sediments

Author(s): Peng, Xuefeng; Ji, Qixing; Angell, John H; Kearns, Patrick J; Yang, Hannah J; et al

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Abstract: Salt marshes provide numerous valuable ecological services. In particular, nitrogen (N) removal in salt marsh sediments alleviates N loading to the coastal ocean. N removal reduces the threat of eutrophication caused by increased N inputs from anthropogenic sources. It is unclear, however, whether chronic nutrient overenrichment alters the capacity of salt marshes to remove anthropogenic N. To assess the effect of nutrient enrichment on N cycling in salt marsh sediments, we examined important N cycle pathways in experimental fertilization plots in a New England salt marsh. We determined rates of nitrification, denitrification, and dissimilatory nitrate reduction to ammonium (DNRA) using sediment slurry incubations with 15N labeled ammonium or nitrate tracers under oxic headspace (20% oxygen/80% helium). Nitrification and denitrification rates were more than tenfold higher in fertilized plots compared to control plots. By contrast, DNRA, which retains N in the system, was high in control plots but not detected in fertilized plots. The relative contribution of DNRA to total nitrate reduction largely depends on the carbon/nitrate ratio in the sediment. These results suggest that long‐term fertilization shifts N cycling in salt marsh sediments from predominantly retention to removal.
Publication Date: 21-Jul-2016
Citation: Peng, Xuefeng, Qixing Ji, John H. Angell, Patrick J. Kearns, Hannah J. Yang, Jennifer L. Bowen, and Bess B. Ward. "Long‐term fertilization alters the relative importance of nitrate reduction pathways in salt marsh sediments." Journal of Geophysical Research: Biogeosciences 121, no. 8 (2016): 2082-2095. doi:10.1002/2016JG003484.
DOI: doi:10.1002/2016JG003484
ISSN: 2169-8953
EISSN: 2169-8961
Pages: 2082 - 2095
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Geophysical Research: Biogeosciences
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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