Data from: Variation in plastic responses of a globally distributed picoplankton species to ocean acidification

Phytoplankton are the basis of marine food webs, and affect biogeochemical cycles. As CO2 levels increase, shifts in the frequencies and physiology of ecotypes within phytoplankton groups will affect their nutritional value and biogeochemical function. However, studies so far are based on a few representative genotypes from key species. Here, we measure changes in cellular function and growth rate at atmospheric CO2 concentrations predicted for the year 2100 in 16 ecotypes of the marine picoplankton Ostreococcus. We find that variation in plastic responses among ecotypes is on par with published between-genera variation, so the responses of one or a few ecotypes cannot estimate changes to the physiology or composition of a species under CO2 enrichment. We show that ecotypes best at taking advantage of CO2 enrichment by changing their photosynthesis rates most should increase in relative fitness, and so in frequency in a high-CO2 environment. Finally, information on sampling location, and not phylogenetic relatedness, is a good predictor of ecotypes likely to increase in frequency in this system.

浮游植物（phytoplankton）是海洋食物网的核心基础，同时调控生物地球化学循环。随着大气二氧化碳浓度升高，浮游植物类群内各生态型（ecotype）的频率与生理特征发生改变，将影响其营养价值与生物地球化学功能。然而目前已有研究多依托关键物种的少量代表性基因型展开。本研究针对海洋超微型浮游生物奥氏藻属（Ostreococcus）的16个生态型，测定了2100年预测大气二氧化碳浓度条件下其细胞功能与生长速率的变化。研究发现，不同生态型间的可塑性响应变异幅度，与已发表的属间变异水平相当，因此仅通过单个或少数生态型的响应，无法准确预估二氧化碳富集条件下某一物种的生理特征或群落组成变化。结果表明，那些通过最大程度调整光合速率以充分利用二氧化碳富集的生态型，其相对适合度将得到提升，进而在高二氧化碳环境中种群频率上升。最后，在本研究体系中，采样地点信息而非系统发育亲缘关系，可作为预测种群频率将上升的生态型的良好指标。