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首页> 外文期刊>Global Biogeochemical Cycles >Evidence of active dinitrogen fixation in surface waters of the eastern tropical South Pacific during El Ni?o and la Ni?a events and evaluation of its potential nutrient controls
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Evidence of active dinitrogen fixation in surface waters of the eastern tropical South Pacific during El Ni?o and la Ni?a events and evaluation of its potential nutrient controls

机译：厄尔尼诺和拉尼娜事件期间热带东太平洋南太平洋地表水中活性二氮固定的证据及其潜在养分控制的评估

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摘要

Biological N2 fixation rates were quantified in the Eastern Tropical South Pacific (ETSP) during both El Ni?o (February 2010) and La Ni?a (March-April 2011) conditions, and from Low-Nutrient, Low-Chlorophyll (20°S) to High-Nutrient, Low-Chlorophyll (HNLC) (10°S) conditions. N_2 fixation was detected at all stations with rates ranging from 0.01 to 0.88 nmol N L~(-1) d~(-1), with higher rates measured during El Ni?o conditions compared to La Ni?a. High N_2 fixations rates were reported at northern stations (HNLC conditions) at the oxycline and in the oxygen minimum zone (OMZ), despite nitrate concentrations up to 30 μmol L~(-1), indicating that inputs of new N can occur in parallel with N loss processes in OMZs. Water-column integrated N_2 fixation rates ranged from 4 to 53 μmol N m~(-2) d~(-1) at northern stations, and from 0 to 148 μmol m~(-2) d~(-1) at southern stations, which are of the same order of magnitude as N_2 fixation rates measured in the oligotrophic ocean. N_2 fixation rates responded significantly to Fe and organic carbon additions in the surface HNLC waters, and surprisingly by concomitant Fe and N additions in surface waters at the edge of the subtropical gyre. Recent studies have highlighted the predominance of heterotrophic diazotrophs in this area, and we hypothesize that N_2 fixation could be directly limited by inorganic nutrient availability, or indirectly through the stimulation of primary production and the subsequent excretion of dissolved organic matter and/or the formation of micro-environments favorable for heterotrophic N_2 fixation. Key Points High N2 fixation was measured in the OMZ and below the euphotic zoneHigh N2 fixation was measured in water masses with high nitrate concentrationsFe, DOC, and DIN additions through (in)direct mechanism stimulated N2 fixation
机译：在El Ni？o（2010年2月）和La Ni？a（2011年3月至2011年）期间，以及低营养，低叶绿素（20°）条件下，对东部热带南太平洋（ETSP）的生物固氮率进行了量化。 S）到高营养，低叶绿素（HNLC）（10°S）的条件。在所有站点上都检测到N_2固定，比率范围为0.01至0.88 nmol N L〜（-1）d〜（-1），在El Ni？o条件下测得的比率高于La Ni？a。尽管硝酸盐浓度高达30μmolL〜（-1），但北部北部站（HNLC条件）和氧气最低区（OMZ）的N_2固定率仍很高，这表明新氮的输入可以并行发生OMZ中有N个损失过程。水柱综合N_2固定率在北站为4到53μmolN〜（-2）d〜（-1），在南站为0至148μmolN〜（-2）d〜（-1）站，其数量级与贫营养化海域中的N_2固定率相同。 N_2固着率对HNLC地表水中的Fe和有机碳添加有显着响应，而令人惊讶的是，在亚热带回旋边缘的地表水中伴随有Fe和N的添加。最近的研究强调了异养重氮菌在该地区的优势，我们假设N_2的固定可能直接受到无机养分利用率的限制，或者间接地通过刺激初级生产和随后排泄的溶解有机物和/或有机物的形成而受到限制。有利于异养N_2固定的微环境。关键点在OMZ中和在富营养区以下测量了高N2固着性在硝酸盐浓度高的水团中测量了高N2固着性通过（间接）机制刺激的N2固定添加了Fe，DOC和DIN

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