DOI: 10.1002/2014GB005013
Scopus记录号: 2-s2.0-85027932596
论文题名: Isotopic evidence for nitrification in the Antarctic winter mixed layer
作者: Smart S ; M ; , Fawcett S ; E ; , Thomalla S ; J ; , Weigand M ; A ; , Reason C ; J ; C ; , Sigman D ; M
刊名: Global Biogeochemical Cycles
ISSN: 8866236
出版年: 2015
卷: 29, 期: 4 起始页码: 427
结束页码: 445
语种: 英语
英文关键词: Antarctic Zone
; nitrate
; nitrate isotopes
; nitrification
; Southern Ocean
; winter mixed layer
Scopus关键词: isotopic analysis
; mixed layer
; nitrification
; oxygen isotope
; Rayleigh number
; sea ice
; turbulence
; Africa
; Southern Ocean
英文摘要: We report wintertime nitrogen and oxygen isotope ratios (δ15N and δ18O) of seawater nitrate in the Southern Ocean south of Africa. Depth profile and underway surface samples collected in July 2012 extend from the subtropics to just beyond the Antarctic winter sea ice edge. We focus here on the Antarctic region (south of 50.3°S), where application of the Rayleigh model to depth profile δ15N data yields estimates for the isotope effect (the degree of isotope discrimination) of nitrate assimilation (1.6-3.3‰) that are significantly lower than commonly observed in the summertime Antarctic (5-8‰). The δ18O data from the same depth profiles and lateral δ15N variations within the mixed layer, however, imply O and N isotope effects that are more similar to those suggested by summertime data. These findings point to active nitrification (i.e., regeneration of organic matter to nitrate) within the Antarctic winter mixed layer. Nitrite removal from samples reveals a low δ15N for nitrite in the winter mixed layer (-40‰ to -20‰), consistent with nitrification, but does not remove the observation of an anomalously low δ15N for nitrate. The winter data, and the nitrification they reveal, explain the previous observation of an anomalously low δ15N for nitrate in the temperature minimum layer (remnant winter mixed layer) of summertime depth profiles. At the same time, the wintertime data require a low δ15N for the combined organic N and ammonium in the autumn mixed layer that is available for wintertime nitrification, pointing to intense N recycling as a pervasive condition of the Antarctic in late summer. ©2015. American Geophysical Union. All Rights Reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/77985
Appears in Collections: 气候变化事实与影响
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作者单位: Department of Oceanography, University of Cape Town, Rondebosch, South Africa; Department of Geosciences, Princeton University, Princeton, NJ, United States; Ocean Systems and Climate Group, Council for Scientific and Industrial Research, Stellenbosch, South Africa
Recommended Citation:
Smart S,M,, Fawcett S,et al. Isotopic evidence for nitrification in the Antarctic winter mixed layer[J]. Global Biogeochemical Cycles,2015-01-01,29(4)