Bacterioplankton play a critical role in primary production, carbon cycling, and nutrient cycling in the oligotrophic ocean. To investigate the effect of elevated CO₂ and warming on the composition and function of bacterioplankton communities in oligotrophic waters, we performed two trace‐metal clean deck board incubation experiments during the New Zealand GEOTRACES transect of the South Pacific gyre (SPG). High‐throughput amplicon sequencing of the 16S rRNA gene revealed that bacterioplankton community composition was distinct between the fringe and ultra‐oligotrophic centre of the SPG and changed consistently in response to elevated CO₂ at the ultra‐oligotrophic centre but not at the mesotrophic fringe of the SPG. The combined effects of elevated CO₂ and warming resulted in a high degree of heterogeneity between replicate communities. Community‐level protein synthesis rates (³H‐Leucine incorporation) and bacterioplankton abundance were not affected by elevated CO₂ alone or in combination with warming at the fringe or ultra‐oligotrophic centre of the SPG. These data suggest bacterioplankton community responses to elevated CO₂ may be modulated by nutrient regimes in open ocean ecosystems and highlight the need for further investigation in expanding oligotrophic subtropical gyres.

中文翻译：

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贫营养性南太平洋回旋区中微妙的浮游细菌群落对二氧化碳浓度升高和变暖的响应。

细菌浮游生物在贫营养化海洋的初级生产，碳循环和营养循环中起着关键作用。为研究CO ₂升高和变暖对贫营养水域浮游细菌群落组成和功能的影响，我们在新西兰南太平洋环流（SPG）的GEOTRACES样线进行了两次微量金属清洁甲板温育实验。16S rRNA基因的高通量扩增子测序表明，浮游生物群落组成在SPG的边缘和超贫营养中心之间是不同的，并且响应于超贫营养中心的CO ₂升高而持续变化，而在SPG的中营养边缘没有变化SPG。CO ₂升高的综合作用变暖导致复制群落之间高度异质性。社区一级的蛋白质合成速率（掺入³ H-亮氨酸）和浮游细菌的丰度不受单独的CO ₂升高或结合SPG边缘或超贫营养中心变暖的影响。这些数据表明，浮游生物群落对CO ₂升高的反应可能受开放海洋生态系统中的养分制度调节，并强调了在扩大贫营养亚热带回旋流方面需要进一步研究的必要性。