1. Submerged macrophytes are important foundation species that can strongly influence the structure and functioning of aquatic ecosystems, but only little is known about the temporal variation and the timescales of these effects (i.e. from hourly, daily, to monthly).
2. Here, we conducted an outdoor experiment in replicated mesocosms (1,000 L) where we manipulated the presence and absence of macrophytes to investigate the temporal variability of their ecosystem effects. We measured several parameters (chlorophyll‐a, phycocyanin, dissolved organic matter [DOM], and oxygen) with high‐resolution sensors (15‐min intervals) over several months (94 days from spring to autumn), and modelled metabolic rates of each replicate ecosystem in a Bayesian framework. We also implemented a simple model to explore competitive interactions between phytoplankton and macrophytes as a driver of variability in chlorophyll‐a.
3. Over the entire experiment, macrophytes had a positive effect on mean DOM concentration, a negative effect on phytoplankton biomass, and either a weak or no effect on mean metabolic rates, DOM composition, and conductivity. We also found that macrophytes increased the variance of dissolved organic carbon composition and metabolic rates, and, occasionally in the observed period, increased the variance of phytoplankton biomass and conductivity. The observation that macrophytes decreased the mean but increased the variance of phytoplankton biomass was consistent with the model that we implemented.
4. Our high‐resolution time series embedded within a manipulative experiment reveal how a foundation species can affect ecosystem properties and processes that have characteristically different timescales of response to environmental variation. Specifically, our results show how macrophytes can affect short‐term dynamics of algal biomass, while also affecting the seasonal build‐up of DOM and the variance of ecosystem metabolism.

中文翻译：

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淹没的大型植物影响水生生态系统的时间变异性

1. 沉水植物是重要的基础物种，可以极大地影响水生生态系统的结构和功能，但对这些影响的时间变化和时间尺度（即每小时，每天，每月）知之甚少。
2. 在这里，我们在复制的中观世界（1,000升）中进行了一项室外实验，在其中我们操纵了大型植物的存在与否，以研究其生态系统效应的时间变异性。我们用高分辨率的传感器（间隔15分钟）在几个月（春季至秋季的94天）内测量了几个参数（叶绿素a，藻蓝蛋白，溶解性有机物[DOM]和氧气），并对每个代谢率进行了建模在贝叶斯框架中复制生态系统。我们还实现了一个简单的模型，以探索浮游植物与大型植物之间的竞争性相互作用，作为叶绿素a变异性的驱动因素。
3. 在整个实验中，大型植物对平均DOM浓度有积极影响，对浮游植物生物量有负面影响，对平均代谢率，DOM组成和电导率影响很小或没有影响。我们还发现大型植物增加了溶解有机碳成分和代谢速率的变化，并且在观察期内偶尔增加了浮游植物生物量和电导率的变化。大型植物降低了平均值，但增加了浮游植物生物量方差的观察结果与我们实施的模型一致。
4. 我们在操作性实验中嵌入的高分辨率时间序列揭示了基础物种如何影响生态系统特性和过程，这些特性和过程对环境变化的响应具有不同的时标。具体而言，我们的结果表明大型植物如何影响藻类生物量的短期动态，同时还影响DOM的季节性积累和生态系统代谢的变化。