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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/40877

Title: Isotope constraints on particulate nitrogen source and dynamics in the upper water column of the oligotrophic South China Sea
Authors: Shuh-Ji Kao;Jin-Yu Terence Yang;Kon-Kee Liu;Minhan Dai;Wen-Chen Chou;Hui-Ling Lin;Haojia Ren
Contributors: 國立臺灣海洋大學:海洋環境化學與生態研究所
Date: 2012-06-14
Issue Date: 2017-02-07T03:25:00Z
Publisher: Global Biogeochemical Cycles
Abstract: Abstract: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 meanδ15NPN, yet, the mean in the upper 100 m (2.0 to 5.3‰) is consistently smaller than that in the lower 100 m, implying the occurrence of vertical biological fractionation and/or an addition of 15N-depleted N from the atmosphere. Theδ15NPN 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 δ15NPN, and high N* values. N fixation is likely the cause for the intermonsoon δ15NPN lows. The δ15NPNvalues of trapped material at 374 m and 447 m range from 3.3 to 7.3‰ with a flux-weighted mean of 5.6‰ resembling theδ15NO3of upwelled sources. By using a mass-isotope balance model under the assumption of no atmospheric N deposition, we obtained an N fixation input of ∼20 ± 26 mmol N m−2 yr−1. This value accounts for only ∼5–10% of the new production on an annual basis.
Relation: 26(2), pp.1-15
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/40877
Appears in Collections:[海洋環境與生態研究所] 期刊論文

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