Culture experiments with coccolithophore algae—the dominant group of marine calcifying phytoplankton—imply a strong sensitivity in growth rate, degree of cellular calcification, and cell size to changes in the carbon chemistry of their growth environment. These results underpin recent studies that have explored how these physiological parameters have varied on geological time scales, in response to changing surface ocean habitats and the concentrations of carbon in the ocean‐atmosphere system. Here, we add to this work with a study of reticulofenestrid coccolith size—the dominant coccolithophore family of the Cenozoic—over the Oligocene to Early Miocene time interval. We examine sediments from contrasting latitudes and regional environmental settings, comparing sites using coherent, updated age models to distinguish globally synchronous trends in cell size from regional trends. Our results confirm several changes in coccolith size—which is strongly correlated to cell size—that are globally reproducible within the ~1 Myr age uncertainty, including a reduction in mean size by >2 μm from 30.2 to 27 and 24.5 to 23 Ma, and then increase in mean size after 20 Ma. The main difference among regions is the presence/absence of coccoliths larger than 8 μm. We evaluate which scenarios of change in carbon dioxide, temperature, and nutrient availability could have exerted selective pressure on cell size for different size classes to produce the observed size trends at each studied site. These million‐year scale adaptations of ancient coccolithophores contribute to the understanding of phytoplankton physiology in the transition to the modern “icehouse” world.

中文翻译：

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渐新世至中新世早期高CO2世界中含钴石载体大小对选择压力的适应

用海洋藻钙化浮游植物的主要群coccolithophore藻进行的培养实验表明，其生长速度，细胞钙化程度和细胞大小对其生长环境的碳化学变化具有很强的敏感性。这些结果为最近的研究奠定了基础，这些研究探索了这些生理参数如何在地质时标上变化，以响应不断变化的表层海洋生境和海洋-大气系统中碳的浓度。在这里，我们通过对渐新世至中新世时间间隔内的网状雌烯可可脂的尺寸（新生代的主要椰脂体家族）进行研究，从而增加了这项工作。我们会检查来自不同纬度和区域环境设置的沉积物，并使用相干的，更新了年龄模型，以区分区域大小趋势的全球同步趋势。我们的结果证实了在约1 Myr年龄不确定性范围内可重现的可积石大小的一些变化（与细胞大小密切相关），包括平均大小从30.2减小到27和从24.5减小到23 Ma超过2μm，并且然后在20 Ma之后平均大小增加。区域之间的主要区别是是否存在大于8μm的球石。我们评估了二氧化碳，温度和养分利用率变化的哪些情景可能会对不同大小类别的细胞大小产生选择性压力，以在每个研究地点产生观察到的大小趋势。