Phenotypic Variability in the Coccolithophore <i>Emiliania huxleyi</i>

Coccolithophores are a vital part of oceanic phytoplankton assemblages that produce organic matter and calcium carbonate (CaCO3) containing traces of other elements (i.e. Sr and Mg). Their associated carbon export from the euphotic zone to the oceans' interior plays a crucial role in CO2 feedback mechanisms and biogeochemical cycles. The coccolithophore Emiliania huxleyi has been widely studied as a model organism to understand physiological, biogeochemical, and ecological processes in marine sciences. Here, we show the inter-strain variability in physiological and biogeochemical traits in 13 strains of E. huxleyi from various biogeographical provinces obtained from culture collections commonly used in the literature. Our results demonstrate that inter-strain genetic variability has greater potential to induce larger phenotypic differences than the phenotypic plasticity of single strains cultured under a broad range of variable environmental conditions. The range of variation found in physiological parameters and calcite Sr:Ca highlights the need to reconsider phenotypic variability in paleoproxy calibrations and model parameterizations to adequately translate findings from single strain laboratory experiments to the real ocean.颗石藻（Coccolithophore）是海洋浮游植物群落的重要组成类群，其可合成有机质与碳酸钙（CaCO₃），并在其中含有痕量其他元素（如锶Sr与镁Mg）。该类群将碳从真光层（euphotic zone）输送至海洋深部的过程，对二氧化碳反馈机制与生物地球化学循环具有关键作用。赫氏颗石藻（Emiliania huxleyi）作为模式生物，已被广泛应用于海洋科学领域中生理、生物地球化学及生态过程的相关研究。本研究针对13株取自不同生物地理区域、且来自文献中常用培养保藏库的赫氏颗石藻（E. huxleyi），分析了其生理与生物地球化学性状的株间变异。研究结果表明，相较于在大范围可变环境条件下培养的单株藻的表型可塑性（phenotypic plasticity），株间遗传变异更易引发显著的表型差异。本研究在生理参数与方解石锶钙比（Sr:Ca）中观测到的变异范围，凸显了需重新审视古气候代用指标校准（paleoproxy calibrations）与模型参数化（model parameterizations）中的表型变异问题，以便能够将单株藻实验室实验的结果合理外推至真实海洋环境中。