Nitrogen is a major limiting element for biological productivity, and thus understanding past variations in nitrogen cycling is central to understanding past and future ocean biogeochemical cycling, global climate cycles, and biodiversity. Organic nitrogen encapsulated in fossil biominerals is generally protected from alteration, making it an important archive of the marine nitrogen cycle on seasonal to million-year timescales. The isotopic composition of fossil-bound nitrogen reflects variations in the large-scale nitrogen inventory, local sources and processing, and ecological and physiological traits of organisms. The ability to measure trace amounts of fossil-bound nitrogen has expanded with recent method developments. In this article, we review the foundations and ground truthing for three important fossil-bound proxy types: diatoms, foraminifera, and corals. We highlight their utility with examples of high-resolution evidence for anthropogenic inputs of nitrogen to the oceans, glacial–interglacial-scale assessments of nitrogen inventory change, and evidence for enhanced CO2 drawdown in the high-latitude ocean. Future directions include expanded method development, characterization of ecological and physiological variation, and exploration of extended timescales to push reconstructions further back in Earth's history.

中文翻译：

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来自硅藻、有孔虫和珊瑚中化石结合氮同位素的见解

氮是生物生产力的主要限制元素，因此了解过去氮循环的变化对于了解过去和未来的海洋生物地球化学循环、全球气候循环和生物多样性至关重要。封装在化石生物矿物中的有机氮通常不会被改变，使其成为季节性至百万年时间尺度上海洋氮循环的重要档案。化石结合氮的同位素组成反映了大规模氮库存、当地来源和加工以及生物体的生态和生理特征的变化。随着最近方法的发展，测量痕量化石结合氮的能力得到了扩展。在本文中，我们回顾了三种重要的化石代理类型的基础和地面实况：硅藻、有孔虫和珊瑚。我们通过以下例子强调了它们的实用性：人为向海洋输入氮的高分辨率证据、氮库存变化的冰期-间冰期规模评估以及二氧化碳增加的证据2高纬度海洋的水位下降。未来的方向包括扩展方法开发、生态和生理变化的表征，以及探索延长的时间尺度以进一步推动地球历史的重建。