Relative importance of top‐down vs. bottom‐up control of lake phytoplankton vertical distributions varies among fluorescence‐based spectral groups
Relative importance of top‐down vs. bottom‐up control of lake phytoplankton vertical distributions varies among fluorescence‐based spectral groups
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DOI：
10.1002/lno.11465
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发表时间：
2020-06
影响因子：
4.5
通讯作者：
M. Lofton;Taylor H. Leach;B. Beisner;C. Carey
中科院分区：
文献类型：
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作者：
M. Lofton;Taylor H. Leach;B. Beisner;C. Carey
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一直是争论和研究的焦点。然而，很少有研究考虑自上而下与自下而上控制对浮游植物垂直分布和深叶绿素最大值（dcm）特征的相对重要性，更少研究这些驱动因素对多个浮游植物类群的重要性。我们研究了来自51个北温带湖泊的四种浮游植物光谱组的深度剖面，以及一套自上而下（浮游动物）和自下而上（营养、温度和光照）的驱动因素，这些驱动因素在大小、营养状态、光照可用性和热分层梯度上有所不同。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。在不同光谱组中，自上而下控制和自下而上控制的相对重要性各不相同，这与每个光谱组中优势类群的特征有关。浮游动物生物量是褐藻垂直分布的最重要驱动因素，可能是因为这一群体包含高度可食用的分类群（主要是绿藻），而热分层预测了浮力调节蓝藻的垂直分布。我们的工作强调了研究浮游植物群落组成的重要性，以提高对DCM特征和水生系统中浮游植物自上而下与自下而上控制的理解。
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.