The paradox of re-oligotrophication: the role of bottom-up versus top-down controls on the phytoplankton community
The paradox of re-oligotrophication: the role of bottom-up versus top-down controls on the phytoplankton community
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DOI：
10.1111/oik.06399
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发表时间：
2019-11-01
期刊：
影响因子：
3.4
通讯作者：
Hsieh, Chih-hao
中科院分区：
文献类型：
--
作者：
Anneville, Orlane;Chang, Chun-Wei;Hsieh, Chih-hao
在过去的几十年里，浮游植物生物量的增加已被广泛观察到，即使在营养物减少的湖泊中也是如此。然而，导致这一趋势的机制尚不清楚。在此，我们通过量化自下而上与自上而下控制在确定日内瓦湖浮游植物群落生物量中的相对贡献，揭示了潜在的机制。具体来说，我们应用非线性时间序列分析，收敛交叉映射（CCM），通过量化1)环境因素与各种浮游植物组合之间的因果关系，以及2)自下而上，自上而下和环境影响的相对重要性，来解读浮游植物组合自下而上与自上而下的控制程度。研究结果表明，近年来浮游植物总生物量的增加，尽管磷含量减少，但主要是由于浮游植物组合较好地适应了相对低磷浓度和温暖水温的再少营养化环境，而浮游动物放牧对其控制较差。我们的研究结果表明，浮游动物是浮游植物生物量的关键驱动因素，并强烈影响富营养化恢复的动态。因此，我们的浮游植物组合方法结合自上而下与自下而上控制的因果识别，提供了对浮游植物生物量在磷减少的湖泊中可能增加的原因的见解。
Increases in phytoplankton biomass have been widely observed over the past decades, even in lakes experiencing nutrient reduction. However, the mechanisms giving rise to this trend remain unclear. Here, we unveil the potential mechanisms through quantifying the relative contribution of bottom-up versus top-down control in determining biomasses of phytoplankton assemblages in Lake Geneva. Specifically, we apply nonlinear time series analysis, convergent cross mapping (CCM), to decipher the degree of bottom-up versus top-down control among phytoplankton assemblages via quantifying 1) causal links between environmental factors and various phytoplankton assemblages and 2) the relative importance of bottom-up, top-down, and environmental effects. We show that the recent increase in total phytoplankton biomass, albeit with phosphorus reduction, was mainly caused by a particular phytoplankton assemblage which was better adapted to the re-oligotrophicated environment characterized by relatively low phosphorus concentrations and warm water temperature, and poorly controlled by zooplankton grazing. Our findings suggest that zooplankton act as a critical driver of phytoplankton biomass and strongly impact the dynamics of recovery from eutrophication. Therefore, our phytoplankton assemblage approach in combination with causal identification of top-down versus bottom-up controls provides insights into the reason why phytoplankton biomass may increase in lakes undergoing phosphorus reduction.