Ammonium availability in the Late Archaean nitrogen cycle
Ammonium availability in the Late Archaean nitrogen cycle
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DOI：
10.1038/s41561-019-0371-1
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发表时间：
2019-07
影响因子：
18.3
通讯作者：
Jie Yang;C. Junium;N. Grassineau;E. Nisbet;G. Izon;G. Izon;C. Mettam;Anthony J. Martin;Aubrey L. Zerkle
中科院分区：
文献类型：
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作者：
Jie Yang;C. Junium;N. Grassineau;E. Nisbet;G. Izon;G. Izon;C. Mettam;Anthony J. Martin;Aubrey L. Zerkle
氮和磷等必需营养素的生物利用率随着地质时间尺度上地球表面环境的化学演变而波动。然而，地球早期氮循环的演变仍然存在很大的不确定性，特别是它如何以及何时对含氧光合作用的演变做出反应。在这里，我们应用多代理地球化学分析（Fe形态，δ 13 C和δ 15 N），特别保存完好的页岩从约27亿年前的Manjeri形成在Belingwe绿岩带，津巴布韦，以评估地球的早期氮循环的氧化还原状态和破译反馈与行星氧化的初始阶段。这些大陆架沉积物以前与早期蓝藻产氧，并提供了一个直接的测试相冲突的假设有关的氮氧阴离子的重要性，在晚白垩世时代。我们的数据揭示了一个占主导地位的厌氧海洋氮循环，其中充满铵的含铁沃茨是一个短暂的氧气绿洲。在有氧光合作用出现的推动下，初级生产力的提高可能会周期性地加强出口生产，这使得有机物降解过程中水体中铵的积累成为可能。有限的氧气供应可能使上涌的铵到达透光层，为多产的晚白垩世生物圈提供充足的氮。
The bioavailability of essential nutrients such as nitrogen and phosphorus has fluctuated with the chemical evolution of Earth surface environments over geological timescales. However, significant uncertainty remains over the evolution of Earth’s early nitrogen cycle, particularly how and when it responded to the evolution of oxygenic photosynthesis. Here we apply multi-proxy geochemical analyses (Fe speciation, δ13C and δ15N) to exceptionally well-preserved shales from the approximately 2.7 billion year old Manjeri Formation in the Belingwe Greenstone Belt, Zimbabwe, to evaluate the redox status of Earth’s early nitrogen cycle and decipher feedbacks associated with the initial stages of planetary oxygenation. These continental shelf sediments were previously linked to early cyanobacterial oxygen production, and provide a direct test of conflicting hypotheses concerning the importance of nitrogen oxyanions in the Late Archaean era. Our data reveal a dominantly anaerobic marine nitrogen cycle in which ammonium-replete ferruginous waters underlay an ephemeral oxygen oasis. Driven by the emergence of oxygenic photosynthesis, increased primary productivity could have periodically strengthened export production, which allowed for the accumulation of ammonium in the water column during organic matter degradation. Restricted oxygen availability could have allowed the upwelling ammonium to reach the photic zone to provide ample nitrogen to fuel a prolific Late Archaean biosphere.