Rapid changes on nutrient supply and CO₂ concentration that occurred in the northern South China Sea (SCS) during the Early Oligocene, provides an ideal natural laboratory, allowing us to peer into the coccolithophores’ physiology in the geological records. In this study, we established a new nannofossil assemblage index, termed as E* ratio, which is calculated by the relative abundance of eutrophic taxa and meso-oligotrophic taxa (\(E^{\ast}=\frac{e}{e+c}\times 100\), where e is eutrophic taxa, and c is meso-oligotrophic taxa). Eutrophic taxa include small Reticulofenestra, Reticulofenestra lockeri group, Reticulofenestra bisecta group and Coccolithus pelagicus group, while meso-oligotrophic taxa include Cyclicargolithus spp. The E* ratio is well correlated with nutrient proxy during the Early Oligocene, while with different covarying patterns under the higher and lower CO₂ condition. By comparing the assemblage changes to the published data, we suggest that coccolithophores may change the way they use carbon source and nutrient with the decline of CO₂. Furthermore, this implies a possible initiation of the carbon concentrating mechanism.

渐新世早期在南海北部发生的养分供应和CO ₂浓度的快速变化提供了一个理想的自然实验室，使我们能够在地质记录中窥视球墨鱼的生理。在这项研究中，我们建立了一个新的纳米化石集合指数，称为E *比，该指数由富营养类群和中营养类群（\（E ^ {\ ast} = \ frac {e} {e + c} \ times 100 \），其中e是富营养类群，而c是中贫营养类群。富营养类群包括小型网状纲，网状纲，基层纲和远洋的Coccolithus组，而中低营养类群包括Cyclicargolithus spp。的E *比率以及与早期渐期间养分代理相关，而与下较高和较低CO不同共变模式₂的状态。通过将组合变化与已发表的数据进行比较，我们建议，随着CO ₂的减少，球石珊瑚可能会改变其利用碳源和养分的方式。此外，这意味着可能启动碳浓缩机制。