The biological fixation of dinitrogen (N2) by marine microbes called “diazotrophs” sustains ∼50% new production in the ocean, boosting CO2 absorption by photoautotrophs and thus contributing to the mitigation of climate change. New environmental conditions sustaining N2 fixation have been revealed in recent years, enabling more accurate forecasting of future nitrogen inputs and localized hot spots. However, at present the paucity and biased geographical coverage of N2 fixation and diazotroph diversity measurements impede attempts to reconcile global nitrogen budgets with observed rates. Most studies have been conducted at disparate spatiotemporal scales, including: (i) discrete and short duration measurements in small seawater volumes isolated from the environment, and (ii) spatial extrapolations and global models of diazotrophy projected over decades to centuries. We argue that this knowledge gap lies at the fine scales: dynamic seawater structures < 200 km wide and < 2 months lifetime. However, the spatiotemporal resolution of conventional oceanographic cruises, with stations separated by tens to hundreds of kilometers, is too poor to resolve fine scale processes. Bridging this gap requires leveraging high spatiotemporal resolution measurements. Here we present and discuss the advantages and disadvantages of contemporary methods and equipment able to provide high-resolution measurements at sea. We also provide insights into high-resolution sampling approaches to be developed in the near future. Increasing the spatiotemporal resolution of diazotroph activity and diversity will provide more realistic quantifications of nitrogen fluxes in the dynamic ocean.

中文翻译：

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用高分辨率测量弥合固氮菌活动和多样性的时空差距

称为“固氮菌”的海洋微生物对二氮 (N2) 的生物固定维持了海洋中约 50% 的新产量，促进了光合自养生物对二氧化碳的吸收，从而有助于缓解气候变化。近年来已经揭示了维持 N2 固定的新环境条件，从而能够更准确地预测未来的氮输入和局部热点。然而，目前 N2 固定和固氮生物多样性测量的缺乏和有偏见的地理覆盖范围阻碍了将全球氮预算与观察到的速率相协调的尝试。大多数研究是在不同的时空尺度上进行的，包括：(i) 在与环境隔离的小海水体积中进行离散和短时间的测量，(ii) 空间外推和固氮作用的全球模型预测了几十年到几个世纪。我们认为，这种知识差距存在于精细尺度上：动态海水结构 < 200 公里宽，寿命 < 2 个月。然而，常规海洋航行的时空分辨率太差，无法解决精细尺度过程，站点相距数十至数百公里。弥合这一差距需要利用高时空分辨率测量。在这里，我们展示并讨论了能够在海上提供高分辨率测量的当代方法和设备的优缺点。我们还提供了对将在不久的将来开发的高分辨率采样方法的见解。