Temporal variability of nitrogen fixation and particulate nitrogen export at Station ALOHA
Temporal variability of nitrogen fixation and particulate nitrogen export at Station ALOHA
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DOI：
10.1002/lno.10386
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发表时间：
2017-01-01
影响因子：
4.5
通讯作者：
Church, Matthew J.
中科院分区：
文献类型：
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作者：
Boettjer, Daniela;Dore, John E.;Church, Matthew J.
我们提出了近9年（2005年6月至2013年12月）的测量上层海洋（0米至125米）二氮（N-2）固定率，再加上颗粒氮（PN）输出在150米，从站ALOHA（22度45 'N，158度W）在北太平洋副热带环流。在2005年6月至2012年6月期间，基于以气泡形式添加N-15（2）示踪剂来测量N-2固定率。从2012年8月开始，首先将N-15（2）溶解在过滤海水中，随后将富含N-15（2）的水加入到N-2固定培养物中。两种方法之间的直接比较显示了一种强有力的关系，添加N-15（2）富集海水导致的深度积分率比添加N-15（2）气泡所产生的深度积分率大两倍。基于这种关系，我们校正了测量的初始阶段，得到的N-2固定速率在整个时间序列（n = 71）中平均为230 +/- 136 mu molNm（-2）d（-1）。对下沉PN的N-15同位素组成以及同位素质量平衡模型的分析表明，在2006-2013日历年期间，N-2固定支持了PN出口的26-47%。由这些贡献率和测得的N-2固定率得出的N输出量在502 ~ 919 μ molNm（-2）d\（-1）之间，相当于1.5 ~ 2.7 molNm（-2）yr（-1）的群落净生产率（NCP），这与以前对该地点NCP的独立估计一致。
We present nearly 9 yrs (June 2005-December 2013) of measurements of upper-ocean (0 m to 125 m) dinitrogen (N-2) fixation rates, coupled with particulate nitrogen (PN) export at 150 m, from Station ALOHA (22 degrees 45'N, 158 degrees W) in the North Pacific Subtropical Gyre. Between June 2005 and June 2012, N-2 fixation rates were measured based on adding the N-15(2) tracer as a gas bubble. Beginning in August 2012, N-15(2) was first dissolved into filtered seawater and the N-15(2)-enriched water was subsequently added to N-2 fixation incubations. Direct comparisons between methodologies revealed a robust relationship, with the addition of N-15(2)-enriched seawater resulting in twofold greater depth-integrated rates than those derived from adding a N-15(2) gas bubble. Based on this relationship, we corrected the initial period of measurements, and the resulting rates of N-2 fixation averaged 230 +/- 136 mu molNm(-2) d(-1) for the full time series (n = 71). Analysis of the N-15 isotopic composition of sinking PN, together with an isotope mass balance model, revealed that N-2 fixation supported 26-47% of PN export during calendar years 2006-2013. The N export derived from these fractional contributions and measured N-2 fixation rates ranged between 502 and 919 mu molNm(-2) d\(-1), which are equivalent to rates of net community production (NCP) of 1.5 to 2.7 molCm(-2) yr(-1), consistent with previous independent estimates of NCP at this site.