Coccolithophores are a key functional phytoplankton group and produce minute calcite plates (coccoliths) in the sunlit layer of the pelagic ocean. Coccoliths significantly contribute to the sediment record since the Triassic and their geometry have been subject to palaeoceanographic and biological studies to retrieve information on past environmental conditions. Here, we present a comprehensive analysis of coccolith, coccosphere and cell volume data of the Southern Ocean Emiliania huxleyi ecotype A, subject to gradients of temperature, irradiance, carbonate chemistry and macronutrient limitation. All tested environmental drivers significantly affect coccosphere, coccolith and cell volume with driver‐specific sensitivities. However, a highly significant correlation emerged between cell and coccolith volume with V_coccolith = 0.012 ± 0.001 * V_cell + 0.234 ± 0.066 (n = 23, r² = .85, p < .0001, σ_est = 0.127), indicating a primary control of coccolith volume by physiological modulated changes in cell volume. We discuss the possible application of fossil coccolith volume as an indicator for cell volume/size and growth rate and, additionally, illustrate that macronutrient limitation of phosphorus and nitrogen has the predominant influence on coccolith volume in respect to other environmental drivers. Our results provide a solid basis for the application of coccolith volume and geometry as a palaeo‐proxy and shed light on the underlying physiological reasons, offering a valuable tool to investigate the fossil record of the coccolithophore E. huxleyi.

中文翻译：

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南大洋巨球藻Emiliania huxleyi的巨球藻数量可能是古细胞数量的指标。

球墨镜藻是重要的功能性浮游植物群，在中上层海洋的阳光照射下会产生微小的方解石板（椰壳石）。由于三叠纪及其几何结构已经接受了古海洋学和生物学研究，以检索有关过去环境条件的信息，因此可可石对泥沙记录有重要贡献。在这里，我们对南大洋Emililiania huxleyi的球藻，球藻和细胞体积数据进行全面分析生态型A，受温度，辐照度，碳酸盐化学物质和大量营养素限制的梯度影响。所有经过测试的环境驱动因素都具有特定于驱动因素的敏感性，对球囊，球囊和细胞体积产生重大影响。然而，高度显著相关细胞和颗石体积之间出现了V_颗石 = 0.012±0.001 *  V_细胞 + 0.234±0.066（N = 23，- [R ²  = 0.85，p  <0.0001，σ _EST = 0.127），表明通过生理调节的细胞体积变化可控制椰菜体积。我们讨论了化石cococolith体积作为细胞体积/大小和生长速率的指标的可能应用，此外，相对于其他环境驱动因素，磷和氮的宏观营养限制对cococolith体积有主要影响。我们的研究结果提供了颗石的体积和几何形状的应用程序作为古代理了坚实的基础，对底层生理原因阐明，提供一个有价值的工具，调查颗石的化石记录E.贺胥。