Adaptation of cell populations to environmental changes is mediated by phenotypic variability at the single-cell level. Enzyme activity is a key factor in cell phenotype and the expression of the alkaline phosphatase activity (APA) is a fundamental phytoplankton strategy for maintaining growth under phosphate-limited conditions. Our aim was to compare the APA among cells and species revived from sediments of the Bay of Brest (Brittany, France), corresponding to a pre-eutrophication period (1940’s) and a beginning of a post-eutrophication period (1990’s) during which phosphate concentrations have undergone substantial variations. Both toxic marine dinoflagellate Alexandrium minutum and the non-toxic dinoflagellate Scrippsiella acuminata were revived from ancient sediments. Using microfluidics, we measured the kinetics of APA at the single-cell level. Our results indicate that all S. acuminata strains had significantly higher APA than A. minutum strains. For both species, the APA in the 1990’s decade was significantly lower than in the 1940’s. For the first time, our results reveal both inter and intraspecific variabilities of dinoflagellate APA and suggest that, at a half-century timescale, two different species of dinoflagellate may have undergone similar adaptative evolution to face environmental changes and acquire ecological advantages.

细胞群对环境变化的适应是由单细胞水平的表型变异性介导的。酶活性是细胞表型的关键因素，碱性磷酸酶活性 (APA) 的表达是浮游植物在磷酸盐限制条件下维持生长的基本策略。我们的目的是比较从布雷斯特湾（法国布列塔尼）的沉积物中恢复的细胞和物种之间的 APA，对应于富营养化前时期（1940 年代）和富营养化后时期（1990 年代）的开始，在此期间磷酸盐浓度发生了很大的变化。有毒的海洋甲藻Alexandrium minutum和无毒的甲藻Scrippsiella acuminata是从古老的沉积物中复活的。使用微流体，我们在单细胞水平上测量了 APA 的动力学。我们的结果表明，所有S. acuminata菌株的 APA 显着高于A. minutum菌株。对于这两个物种，1990 年代十年的 APA 明显低于 1940 年代。我们的研究结果首次揭示了甲藻 APA 的种间和种内变异性，并表明在半个世纪的时间尺度上，两种不同的甲藻可能经历了相似的适应进化，以应对环境变化并获得生态优势。