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Influence of open ocean nitrogen supply on the skeletal δ15N of modern shallow-water scleractinian corals

Author(s): Wang, Xingchen T; Sigman, Daniel M; Cohen, Anne L; Sinclair, Daniel J; Sherrell, Robert M; et al

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Abstract: The isotopic composition of skeleton-bound organic nitrogen in shallow-water scleractinian corals (hereafter, CS-δ15N) is an emerging tool for studying the marine nitrogen cycle in the past. The CS-δ15N has been shown to reflect the δ15N of nitrogen (N) sources to corals, with most applications to date focusing on the anthropogenic/terrestrial N inputs to reef environments. However, many coral reefs receive their primary N sources from the open ocean, and the CS-δ15N of these corals may provide information on past changes in the open ocean regional and global N cycle. Using a recently developed persulfate/denitrifier-based method, we measured CS-δ15N in modern shallow-water scleractinian corals from 8 sites proximal to the open ocean. At sites with low open ocean surface nitrate concentrations typical of the subtropics and tropics, measured CS-δ15N variation on seasonal and annual timescales is most often less than 2‰. In contrast, a broad range in CS-δ15N (of ∼10‰) is measured across these sites, with a strong correlation between CS-δ15N and the δ15N of the deep nitrate supply to the surface waters near the reefs. While CS-δ15N can be affected by other N sources as well and can vary in response to local reef conditions as well as coral/symbiont physiological changes, this survey indicates that, when considering corals proximal to the open ocean, the δ15N of the subsurface nitrate supply to surface waters drives most of the CS-δ15N variation across the global ocean. Thus, CS-δ15N is a promising proxy for reconstructing the open ocean N cycle in the past.
Publication Date: 1-May-2016
Electronic Publication Date: 9-Mar-2016
Citation: Wang, Xingchen T., Daniel M. Sigman, Anne L. Cohen, Daniel J. Sinclair, Robert M. Sherrell, Kim M. Cobb, Dirk V. Erler, Jarosław Stolarski, Marcelo V. Kitahara, and Haojia Ren. "Influence of open ocean nitrogen supply on the skeletal δ15N of modern shallow-water scleractinian corals." Earth and Planetary Science Letters 441 (2016): 125-132. doi:10.1016/j.epsl.2016.02.032.
DOI: doi:10.1016/j.epsl.2016.02.032
ISSN: 0012-821X
Pages: 125 - 132
Type of Material: Journal Article
Journal/Proceeding Title: Earth and Planetary Science Letters
Version: Author's manuscript

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