Phytoplankton form the base of most marine trophic chains and studying their past diversity at regional and global scales can provide valuable insights into the evolution of marine ecosystems and climate history. Using a new database of more than 4000 species of acritarchs and prasinophytes, a comprehensive investigation of the taxonomic diversity trajectories of this marine (micro)phytoplankton throughout the Paleozoic is performed for the first time. This dataset compiles data from published literature, including taxonomic, geographic and stratigraphic information at the stage resolution. Our results highlight five major temporal trends in phytoplankton diversity variation: (i) an initial plateau of moderate richness during the early and middle Cambrian, followed by (ii) a sharp increase from the late Cambrian to the Middle Ordovician, which records the highest Paleozoic diversity of organic-walled phytoplankton (OWP); then, (iii) a protracted decrease during the Late Ordovician to Middle Devonian; (iv) a slight peak in diversity during the Late Devonian, before (v) falling to the lowest richness recorded during the Carboniferous and Permian. The role of phytoplankton during major biotic events is discussed: While phytoplankton evolution may have been a factor in enabling the “Cambrian Explosion”, we do not find a strong relationship between the diversity changes of the phytoplankton and this event and we thus refute the notion that it might have been a major driver of radiations during this interval. However, a strong increase in phytoplankton diversity coincides with the Great Ordovician Biodiversification Event (GOBE), indicating that the profound changes of marine phytoplankton, and thus of the base of marine food webs, enabled diversifications throughout marine ecosystems. A decrease in phytoplankton diversity during the Lower and Middle Devonian points against the hypothesis of phytoplankton triggering the proposed “Devonian Nekton Revolution”. By comparing the results with paleoenvironmental parameters, several factors are found to be possibly related to the long-term diversity trends: Our results indicate that paleogeography and sea-level changes were probably the main drivers of phytoplankton diversity patterns throughout the Paleozoic, while increases in sediment influx provided facilitating conditions for phytoplankton diversification. Atmospheric CO₂ concentration as well as temperature and related sea ice cover are found to be further important controlling factors for phytoplankton diversity.

浮游植物是大多数海洋营养链的基础，在区域和全球范围内研究它们过去的多样性可以为海洋生态系统的演变和气候历史提供有价值的见解。使用一个包含 4000 多种 acritarchs 和 prasinophytes 的新数据库，首次对整个古生代的这种海洋（微）浮游植物的分类多样性轨迹进行了全面调查。该数据集汇编了已发表文献中的数据，包括阶段分辨率的分类、地理和地层信息。我们的研究结果突出了浮游植物多样性变化的五个主要时间趋势：（i）在早寒武世和中寒武世期间出现中等丰富度的初始高原，其次是（ii）从晚寒​​武世到寒武世急剧增加中奥陶世，记录了古生代有机壁浮游植物（OWP）的最高多样性；然后，（iii）晚奥陶世至中泥盆世的长期减少；(iv) 晚泥盆世的多样性略有高峰，之后 (v) 下降到石炭纪和二叠纪记录的最低丰富度。讨论了浮游植物在重大生物事件中的作用：虽然浮游植物进化可能是促成“寒武纪大爆发”的一个因素，但我们没有发现浮游植物的多样性变化与这一事件之间存在密切关系，因此我们驳斥了这一观点在此期间，它可能是辐射的主要驱动因素。然而，浮游植物多样性的强劲增长恰逢大奥陶纪生物多样性事件 (GOBE)，表明海洋浮游植物的深刻变化以及海洋食物网基础的变化，使整个海洋生态系统的多样性成为可能。下泥盆纪和中泥盆纪浮游植物多样性的减少与浮游植物引发拟议的“泥盆纪尼克生物革命”的假设背道而驰。通过将结果与古环境参数进行比较，发现几个因素可能与长期多样性趋势有关：我们的结果表明，古地理和海平面变化可能是整个古生代浮游植物多样性模式的主要驱动力，而增加沉积物流入为浮游植物多样化提供了便利条件。大气二氧化碳₂浓度以及温度和相关的海冰覆盖被发现是浮游植物多样性的进一步重要控制因素。