Dinitrogen (N₂) fixation is an important source of biologically reactive nitrogen (N) to the global ocean. The magnitude of this flux, however, remains uncertain, in part because N₂ fixation rates have been estimated following divergent protocols and because associated levels of uncertainty are seldom reported—confounding comparison and extrapolation of rate measurements. A growing number of reports of relatively low but potentially significant rates of N₂ fixation in regions such as oxygen minimum zones, the mesopelagic water column of the tropical and subtropical oceans, and polar waters further highlights the need for standardized methodological protocols for measurements of N₂ fixation rates and for calculations of detection limits and propagated error terms. To this end, we examine current protocols of the ¹⁵N₂ tracer method used for estimating diazotrophic rates, present results of experiments testing the validity of specific practices, and describe established metrics for reporting detection limits. We put forth a set of recommendations for best practices to estimate N₂ fixation rates using ¹⁵N₂ tracer, with the goal of fostering transparency in reporting sources of uncertainty in estimates, and to render N₂ fixation rate estimates intercomparable among studies.

中文翻译：

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对15N2示踪法测量中上层生态系统中重氮养分生产的评论

固氮（N ₂）是向全球海洋输送生物活性氮（N）的重要来源。但是，这种通量的大小仍然不确定，部分原因是根据不同的方案估算了N ₂固定率，并且很少报告相关的不确定性水平，从而混淆了速率测量的比较和推断。越来越多的报告指出，在诸如氧气最低限度区域，热带和亚热带海洋的中生水柱以及极地水域等地区，N ₂固着率相对较低，但潜力可能很大，这进一步凸显了对用于测量N的标准化方法学方案的需求₂固定率，用于计算检测限和传播的误差项。为此，我们检查了用于估计重氮营养率的¹⁵ N ₂示踪剂方法的当前方案，介绍了测试特定方法的有效性的实验结果，并描述了报告检测限的已建立指标。我们提出了一组最佳实践建议，以使用¹⁵ N ₂示踪剂估算N ₂固定率，目的是提高报告不确定性来源的报告的透明度，并使N ₂固定率的估计在研究之间可比。