Subtropical gyres cover 26%–29% of the world's surface ocean and are conventionally regarded as ocean deserts due to their permanent stratification, depleted surface nutrients, and low biological productivity. Despite tremendous advances over the past three decades, particularly through the Hawaii Ocean Time-series and the Bermuda Atlantic Time-series Study, which have revolutionized our understanding of the biogeochemistry in oligotrophic marine ecosystems, the gyres remain understudied. We review current understanding of upper ocean biogeochemistry in the North Pacific Subtropical Gyre, considering other subtropical gyres for comparison. We focus our synthesis on spatial variability, which shows larger than expected dynamic ranges of properties such as nutrient concentrations, rates of N₂ fixation, and biological production. This review provides new insights into how nutrient sources drive community structure and export in upper subtropical gyres. We examine the euphotic zone (EZ) in subtropical gyres as a two-layered vertically structured system: a nutrient-depleted layer above the top of the nutricline in the well-lit upper ocean and a nutrient-replete layer below in the dimly lit waters. These layers vary in nutrient supply and stoichiometries and physical forcing, promoting differences in community structure and food webs, with direct impacts on the magnitude and composition of export production. We evaluate long-term variations in key biogeochemical parameters in both of these EZ layers. Finally, we identify major knowledge gaps and research challenges in these vast and unique systems that offer opportunities for future studies.

中文翻译：

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寡营养北太平洋副热带环流的上层海洋生物地球化学：从营养源到碳输出

副热带环流覆盖了世界海洋表面的26%–29%，由于其永久分层、表面营养物质枯竭和生物生产力低下，通常被视为海洋沙漠。尽管过去三十年取得了巨大进步，特别是通过夏威夷海洋时间序列和百慕大大西洋时间序列研究，彻底改变了我们对寡营养海洋生态系统生物地球化学的理解，但对环流的研究仍然不足。我们回顾了目前对北太平洋副热带环流上层海洋生物地球化学的认识，并考虑其他副热带环流进行比较。我们将合成重点放在空间变异上，这显示出大于预期的动态特性范围，例如养分浓度、N _2比率固定和生物生产。这篇综述提供了关于营养物来源如何驱动上亚热带环流群落结构和输出的新见解。我们将亚热带环流中的富光层（EZ）视为一个两层垂直结构系统：在光线充足的上层海洋中营养线顶部上方的营养耗尽层和在光线昏暗的水域下方的营养丰富层。这些层在养分供应、化学计量和物理强迫方面各不相同，促进了群落结构和食物网的差异，对出口生产的规模和构成产生直接影响。我们评估了这两个 EZ 层中关键生物地球化学参数的长期变化。最后，