Although the general impacts of zooplankton grazing on phytoplankton communities are clear, we know comparatively less about how specific grazing strategies interact with environmental conditions to shape the size structure of phytoplankton communities. Here, we present a new data‐driven, size‐based model that describes changes in the size composition of lake phytoplankton under various environmental constraints. The model includes an ecological trade‐off emerging from observed allometric relationships between (1) phytoplankton cell size and phytoplankton growth and (2) phytoplankton cell size and zooplankton grazing. In our model, phytoplankton growth is nutrient‐dependent and zooplankton grazing varies according to specific grazing strategies, namely, specialists (targeting a narrow range of the size‐feeding spectrum) vs. generalists (targeting a wide range of the size‐feeding spectrum). Our results indicate that grazing strategies shape the size composition of the phytoplankton community in nutrient‐rich conditions, whereas inorganic nutrient concentrations govern phytoplankton biomass. Under oligotrophic regimes, the phytoplankton community is dominated by small cell sizes and the grazers have little to no impact. Under eutrophic regimes, dominating specialist grazers push phytoplankton towards small cells, whereas dominating generalist grazers push phytoplankton towards large cells. Our work highlights that trait‐based modeling, based on realistic eco‐physiological trade‐offs, represents a valuable tool for disentangling the interactive roles played by nutrient regimes and grazing strategies in determining the size compositions of lake phytoplankton. Ultimately, our study offers a quantitative basis for understanding how communities of lake phytoplankton may reorganize in the future in response to changes in nutrient levels and zooplankton grazing strategies.

中文翻译：

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放牧策略决定富营养化湖泊中浮游植物的大小组成

尽管浮游动物放牧对浮游植物群落的总体影响是明确的，但我们对具体放牧策略如何与环境条件相互作用以塑造浮游植物群落规模结构的了解相对较少。在这里，我们提出了一种新的数据驱动的、基于尺寸的模型，该模型描述了各种环境限制下湖泊浮游植物尺寸组成的变化。该模型包括从观察到的（1）浮游植物细胞大小和浮游植物生长和（2）浮游植物细胞大小和浮游动物放牧之间的异速生长关系中出现的生态权衡。在我们的模型中，浮游植物的生长依赖于营养，浮游动物的放牧根据具体的放牧策略而变化，即专家（针对较小的尺寸摄食范围）与通才（针对较宽的尺寸摄食范围） 。我们的结果表明，放牧策略决定了营养丰富条件下浮游植物群落的规模组成，而无机养分浓度则决定了浮游植物的生物量。在寡营养状态下，浮游植物群落以小细胞为主，食草动物几乎没有影响。在富营养化状况下，占主导地位的专科食草动物将浮游植物推向小细胞，而占主导地位的通才食草动物将浮游植物推向大细胞。我们的工作强调，基于现实的生态生理权衡的基于性状的模型是一个有价值的工具，可以解开营养状况和放牧策略在确定湖泊浮游植物大小组成方面所发挥的相互作用。最终，我们的研究为了解湖泊浮游植物群落未来如何重组以应对营养水平和浮游动物放牧策略的变化提供了定量基础。