Mesozooplankton play a key role in marine ecosystems as they modulate the transfer of energy from phytoplankton to large marine organisms. In addition, they directly influence the oceanic cycles of carbon and nutrients through vertical migrations, fecal pellet production, respiration, and excretion. Mesozooplankton are mainly made up of metazoans, which undergo important size changes during their life cycle, resulting in significant variations in metabolic rates. However, most marine biogeochemical models represent mesozooplankton as protists-like organisms. Here, we study the potential caveats of this simplistic representation by using a chemostat-like zero-dimensional model with four different Nutrient-Phytoplankton-Zooplankton configurations in which the description of mesozooplankton ranges from protist-type organisms to using a size-based formulation including explicit reproduction and ontogenetic growth. We show that the size-based formulation strongly impacts mesozooplankton. First, it generates a delay of a few months in the response to an increase in food availability. Second, the increase in mesozooplankton biomass displays much larger temporal variations, in the form of successive cohorts, because of the dependency of the ingestion rate to body size. However, the size-based formulation does not affect smaller plankton or nutrient concentrations. A proper assessment of these top-down effects would require implementing our size-resolved approach in a 3-dimensional biogeochemical model. Furthermore, the bottom-up effects on higher trophic levels resulting from the significant changes in the temporal dynamics of mesozooplankton could be estimated in an end-to-end model coupling low and high trophic levels.

中浮游动物在海洋生态系统中发挥着关键作用，因为它们调节能量从浮游植物到大型海洋生物的转移。此外，它们通过垂直迁移、粪便颗粒产生、呼吸和排泄直接影响碳和养分的海洋循环。中浮游动物主要由后生动物组成，它们在生命周期中经历了重要的大小变化，导致代谢率发生显着变化。然而，大多数海洋生物地球化学模型将中型浮游动物表示为类原生生物。这里，我们通过使用具有四种不同营养 - 浮游植物 - 浮游动物配置的类似恒化器的零维模型来研究这种简单表示的潜在警告，其中中浮游动物的描述范围从原生生物类型到使用基于大小的公式，包括显式繁殖和个体发育。我们表明基于尺寸的公式强烈影响中浮游动物。首先，它会延迟几个月对粮食供应增加的反应。其次，中型浮游生物生物量的增加以连续队列的形式显示出更大的时间变化，因为摄入率与体型有关。然而，基于尺寸的配方不会影响较小的浮游生物或营养浓度。对这些自上而下的影响的正确评估需要在 3 维生物地球化学模型中实施我们的尺寸分辨方法。此外，可以在耦合低营养级和高营养级的端到端模型中估计中型浮游动物时间动态的显着变化对更高营养级的自下而上的影响。