Abstract Despite their critical role as the main energy pathway between phytoplankton and fish, the functional complexity of zooplankton is typically poorly resolved in marine ecosystem models. Trait-based approaches—where zooplankton are represented with functional traits such as body size—could help improve the resolution of zooplankton in marine ecosystem models and their role in trophic transfer and carbon sequestration. Here, we present the Zooplankton Model of Size Spectra version 2 (ZooMSSv2), a functional size-spectrum model that resolves nine major zooplankton functional groups (heterotrophic flagellates, heterotrophic ciliates, larvaceans, omnivorous copepods, carnivorous copepods, chaetognaths, euphausiids, salps and jellyfish). Each group is represented by the functional traits of body size, size-based feeding characteristics and carbon content. The model is run globally at 5° resolution to steady-state using long-term average temperature and chlorophyll a for each grid-cell. Zooplankton community composition emerges based on the relative fitness of the different groups. Emergent steady-state patterns of global zooplankton abundance, biomass and growth rates agree well with empirical data, and the model is robust to changes in the boundary conditions of the zooplankton. We use the model to consider the role of the zooplankton groups in supporting higher trophic levels, by exploring the sensitivity of steady-state fish biomass to the removal of individual zooplankton groups across the global ocean. Our model shows zooplankton play a key role in supporting fish biomass in the global ocean. For example, the removal of euphausiids or omnivorous copepods caused fish biomass to decrease by up to 80%. By contrast, the removal of carnivorous copepods caused fish biomass to increase by up to 75%. Our results suggest that including zooplankton complexity in ecosystem models could be key to better understanding the distribution of fish biomass and trophic efficiency across the global ocean.

中文翻译：

---

解析浮游动物组成的全球海洋生态系统的功能尺寸谱模型

摘要 尽管浮游动物作为浮游植物和鱼类之间的主要能量途径发挥着重要作用，但浮游动物的功能复杂性在海洋生态系统模型中通常很难解决。基于特征的方法——其中浮游动物用身体大小等功能特征表示——可以帮助提高浮游动物在海洋生态系统模型中的分辨率及其在营养转移和碳固存中的作用。在这里，我们展示了尺寸谱版本 2 (ZooMSSv2) 的浮游动物模型，这是一种功能性尺寸谱模型，可解析九个主要的浮游动物功能组（异养鞭毛虫、异养纤毛虫、幼虫、杂食性桡足类动物、肉食性桡足类动物、毛颌类动物、梭鱼属海蜇）。每组由体型的功能特征代表，基于尺寸的饲养特性和碳含量。该模型使用每个网格单元的长期平均温度和叶绿素 a 以 5° 分辨率全局运行到稳态。浮游动物群落组成基于不同群体的相对适应度而出现。全球浮游动物丰度、生物量和增长率的紧急稳态模式与经验数据非常吻合，并且该模型对浮游动物边界条件的变化具有鲁棒性。我们使用该模型来考虑浮游动物群在支持更高营养水平方面的作用，通过探索稳态鱼类生物量对去除全球海洋中单个浮游动物群的敏感性。我们的模型显示浮游动物在支持全球海洋中的鱼类生物量方面发挥着关键作用。例如，去除磷虾或杂食性桡足类动物导致鱼类生物量减少多达 80%。相比之下，肉食性桡足类动物的去除导致鱼类生物量增加了 75%。我们的研究结果表明，将浮游动物复杂性纳入生态系统模型可能是更好地了解全球海洋鱼类生物量和营养效率分布的关键。