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	Isotope constraints on particulate nitrogen source and dynamics in the upper water column of the oligotrophic South China Sea
	Kao, Shuh-Ji ; Yang, Jin-Yu Terence ; Liu, Kon-Kee ; Dai, Minhan ; Dai MH(戴民汉) ; Chou, Wen-Chen ; Lin, Hui-Ling ; Ren, Haojia
	2012-06-14
关键词	N-2 FIXATION PACIFIC-OCEAN CYANOBACTERIUM TRICHODESMIUM MARINE CYANOBACTERIUM SINKING PARTICLES STABLE NITROGEN ORGANIC-MATTER TIME-SERIES NITRATE CARBON
英文摘要	Particulate nitrogen (PN) dynamics in the oligotrophic northern South China Sea (around the SouthEast Asian Time-series Study (SEATS) station) was explored by examining the isotopic compositions of suspended PN in the top 200 m over 3 years and sinking PN collected by sediment traps. The PN inventory (IPN) in the upper 100 m is larger than in the lower 100 m, exhibiting stronger seasonality. Both layers reveal significant seasonality in mean delta N-15(PN), yet, the mean in the upper 100 m (2.0 to 5.3 parts per thousand) is consistently smaller than that in the lower 100 m, implying the occurrence of vertical biological fractionation and/or an addition of N-15-depleted N from the atmosphere. The delta N-15(PN) surges in winter, when the mixed layer is deeper, indicate an intensified nitrate supply from thermocline, during which relatively stronger downward transfer efficiency was inferred by a small IPN gradient. The largest vertical gradient in IPN appeared during intermonsoon periods, corresponding with weak vertical mixing, low delta N-15(PN), and high N* values. N fixation is likely the cause for the intermonsoon delta N-15(PN) lows. The delta N-15(PN) values of trapped material at 374 m and 447 m range from 3.3 to 7.3 parts per thousand with a flux-weighted mean of 5.6 parts per thousand resembling the delta(NO3)-N-15 of upwelled sources. By using a mass-isotope balance model under the assumption of no atmospheric N deposition, we obtained an N fixation input of similar to 20 +/- 26 mmol N m(-2) yr(-1). This value accounts for only similar to 5-10% of the new production on an annual basis.; Taiwan [NSC 98-2116-M-001-005]; Academia Sinica Thematic Program AFOBi; China (973 Program) [2009CB421200]; Introducing Talents of Discipline to Universities [B07034]
语种	英语
出版者	AMER GEOPHYSICAL UNION
内容类型	期刊论文
源URL	[http://dx.doi.org/10.1029/2011GB004091]
专题	海洋环境－已发表论文
推荐引用方式 GB/T 7714	Kao, Shuh-Ji,Yang, Jin-Yu Terence,Liu, Kon-Kee,et al. Isotope constraints on particulate nitrogen source and dynamics in the upper water column of the oligotrophic South China Sea[J],2012.
APA	Kao, Shuh-Ji.,Yang, Jin-Yu Terence.,Liu, Kon-Kee.,Dai, Minhan.,戴民汉.,...&Ren, Haojia.(2012).Isotope constraints on particulate nitrogen source and dynamics in the upper water column of the oligotrophic South China Sea..
MLA	Kao, Shuh-Ji,et al."Isotope constraints on particulate nitrogen source and dynamics in the upper water column of the oligotrophic South China Sea".(2012).

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