Nitrogen fixation in denitrified marine waters.
Nitrogen fixation in denitrified marine waters.
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DOI：
10.1371/journal.pone.0020539
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发表时间：
2011
期刊：
影响因子：
3.7
通讯作者：
Ulloa O
中科院分区：
文献类型：
--
作者：
Fernandez C;Farías L;Ulloa O
固氮是将大气中的氮气生物转化为氨的一个基本过程，从而补偿通过反硝化和厌氧氨氧化产生的氮素损失。目前，这些过程造成的氮向海洋的输入和损失被认为是在空间上分开的：氮固定主要发生在开阔的海洋环境中(主要通过重氮营养的蓝藻)，而氮的损失发生在耗氧的中间水域和沉积物中(主要通过反硝化和厌氧氨氧化细菌)。在这里，我们报告了2005年和2007年在热带南太平洋东部(ETSP)的两次海洋巡航中获得的固氮率，该地区的特点是存在沿海上升流和一个主要的永久性氧气最小区(OMZ)。我们的结果显示了显著的水柱固氮速率；然而，从表层到120m的积分速率在两次航行之间因∼而变化30倍(7.5±4.6vs190±82.3umolm−2d−1)。此外，2007年对400m深度的速率进行了测量，结果表明，亚表面缺氧层对积分速率的贡献(574±294µmolm−2 d−1)是氧化真光层(48±68µmolm−2 d−1)的5倍。同时分子检测在地表水和地下水中检测到二氮原酶还原酶基因nifH。NifH序列的系统发育分析表明，在测得的固氮率最高的时候，存在一个多样化的重氮群落。因此，我们的结果表明，在营养丰富的沿海上升流系统中发生了固氮作用，更重要的是，在底层的OMZ中发生了固氮作用。他们还表明，固氮是一个广泛的过程，可以零星地为这些地区提供固定氮的补充来源。
Nitrogen fixation is an essential process that biologically transforms atmospheric dinitrogen gas to ammonia, therefore compensating for nitrogen losses occurring via denitrification and anammox. Currently, inputs and losses of nitrogen to the ocean resulting from these processes are thought to be spatially separated: nitrogen fixation takes place primarily in open ocean environments (mainly through diazotrophic cyanobacteria), whereas nitrogen losses occur in oxygen-depleted intermediate waters and sediments (mostly via denitrifying and anammox bacteria). Here we report on rates of nitrogen fixation obtained during two oceanographic cruises in 2005 and 2007 in the eastern tropical South Pacific (ETSP), a region characterized by the presence of coastal upwelling and a major permanent oxygen minimum zone (OMZ). Our results show significant rates of nitrogen fixation in the water column; however, integrated rates from the surface down to 120 m varied by ∼30 fold between cruises (7.5±4.6 versus 190±82.3 µmol m−2 d−1). Moreover, rates were measured down to 400 m depth in 2007, indicating that the contribution to the integrated rates of the subsurface oxygen-deficient layer was ∼5 times higher (574±294 µmol m−2 d−1) than the oxic euphotic layer (48±68 µmol m−2 d−1). Concurrent molecular measurements detected the dinitrogenase reductase gene nifH in surface and subsurface waters. Phylogenetic analysis of the nifH sequences showed the presence of a diverse diazotrophic community at the time of the highest measured nitrogen fixation rates. Our results thus demonstrate the occurrence of nitrogen fixation in nutrient-rich coastal upwelling systems and, importantly, within the underlying OMZ. They also suggest that nitrogen fixation is a widespread process that can sporadically provide a supplementary source of fixed nitrogen in these regions.
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影响因子：
64.8
作者：
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通讯作者：
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影响因子：
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Hamersley, M. Robert;Lavik, Gaute;Kuypers, Marcel M. M.
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Deutsch, Curtis;Sarmiento, Jorge L.;Dunne, John P.
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