The relative importance of top‐down vs. bottom‐up control of phytoplankton biomass in aquatic ecosystems has been long debated and studied. However, few studies have considered the relative importance of top‐down vs. bottom‐up control on phytoplankton vertical distributions and characteristics of deep chlorophyll maxima (DCMs), and fewer still have investigated the importance of these drivers for multiple phytoplankton groups. We examined depth profiles of four phytoplankton spectral groups and a suite of top‐down (zooplankton) and bottom‐up (nutrients, temperature, and light) drivers from 51 north temperate lakes varying on gradients of size, trophic state, light availability, and thermal stratification. We used regression trees to identify the most important drivers of different vertical distribution metrics for each phytoplankton spectral group. The relative importance of top‐down vs. bottom‐up control varied across spectral groups and was related to the characteristics of the dominant taxa within each spectral group, as assessed by microscope counts. Zooplankton biomass was the most important driver of brown algae vertical distributions, likely because this group contained highly edible taxa (primarily chrysophytes), while thermal stratification predicted vertical distributions of buoyancy‐regulating cyanobacteria. Our work highlights the importance of examining phytoplankton community composition to improve understanding of DCM characteristics and top‐down vs. bottom‐up control of phytoplankton in aquatic systems.

中文翻译：

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自上而下与自下而上控制湖泊浮游植物垂直分布的相对重要性在基于荧光的光谱组之间有所不同

在水生生态系统中自上而下与自下而上控制浮游植物生物量的相对重要性已经长期辩论和研究。但是，很少有研究考虑到自上而下与自下而上的控制对浮游植物垂直分布和深层叶绿素最大值（DCM）特征的相对重要性，而很少有人研究这些驱动因素对多个浮游植物群体的重要性。我们研究了来自51个北部温带湖泊的四个浮游植物光谱组的深度剖面以及一组自上而下（浮游动物）和自下而上（营养素，温度和光）驱动因子，其大小，营养状态，光可利用性和热分层。我们使用回归树来确定每个浮游植物光谱组不同垂直分布指标的最重要驱动因素。自上而下与自下而上的控制的相对重要性在各个光谱组之间有所不同，并且与每个光谱组中优势类群的特征相关，如通过显微镜计数所评估的。浮游生物的生物量是褐藻垂直分布的最重要驱动力，这可能是因为该组包含高度可食用的类群（主要是温藻类），而热分层则预测了调节浮力的蓝细菌的垂直分布。我们的工作强调了检查浮游植物群落组成的重要性，以增进对DCM特征以及水生系统中浮游植物自上而下与自下而上的控制的理解。通过显微镜计数评估。浮游动物的生物量是褐藻垂直分布的最重要驱动力，这可能是因为该组中含有大量可食用的类群（主要是温藻类），而热分层则预测了调节浮力的蓝细菌的垂直分布。我们的工作突显了检查浮游植物群落组成的重要性，以增进对水生系统中DCM特征以及浮游植物自上而下与自下而上的控制的理解。通过显微镜计数评估。浮游动物的生物量是褐藻垂直分布的最重要驱动力，这可能是因为该组中含有大量可食用的类群（主要是温藻类），而热分层则预测了调节浮力的蓝细菌的垂直分布。我们的工作突显了检查浮游植物群落组成的重要性，以增进对水生系统中DCM特征以及浮游植物自上而下与自下而上的控制的理解。