Reduced resilience of a globally distributed coccolithophore to ocean acidification: Confirmed up to 2000 generations@en

Ocean acidification (OA), induced by rapid anthropogenic CO2 rise and its dissolution in seawater, is known to have consequences for marine organisms. However, knowledge on the evolutionary responses of phytoplankton to OA has been poorly studied. Here we examined the coccolithophore Gephyrocapsa oceanica, while growing it for 2000 generations under ambient and elevated CO2 levels. While OA stimulated growth in the earlier selection period (from generations 700 to 1550), it reduced it in the later selection period up to 2000 generations. Similarly, stimulated production of particulate organic carbon and nitrogen reduced with increasing selection period and decreased under OA up to 2000 generations. The specific adaptation of growth to OA disappeared in generations 1700 to 2000 when compared with that at 1000 generations. Both phenotypic plasticity and fitness decreased within selection time, suggesting that the species' resilience to OA decreased after 2000 generations under high CO2 selection.由人为活动快速推高二氧化碳浓度并使其溶解于海水所引发的海洋酸化（Ocean Acidification, OA），已知会对海洋生物造成诸多不利影响。然而，目前关于浮游植物对海洋酸化的演化响应的相关研究仍较为匮乏。本研究选取颗石藻（coccolithophore）大洋桥石藻（Gephyrocapsa oceanica）作为研究对象，在环境二氧化碳水平与升高二氧化碳水平两种培养条件下，对其开展了长达2000代的继代培养并进行相关检测。在选择培养的早期阶段（第700代至第1550代），海洋酸化可促进藻株生长；但在直至第2000代的后期选择阶段，藻株生长反而受到抑制。类似地，原本受海洋酸化诱导提升的颗粒有机碳与颗粒氮产量，随选择培养周期的延长而逐步降低；且在直至第2000代的整个培养过程中，该产量在海洋酸化条件下均呈下降趋势。与第1000代时的表型相比，藻株生长对海洋酸化的特异性适应在第1700代至第2000代期间完全消失。表型可塑性与适合度均随选择培养时长的增加而下降，这表明在高二氧化碳选择压力下连续培养2000代后，该物种对海洋酸化的耐受能力有所降低。