Community and ecosystem dynamics of north temperate shallow lakes during the Anthropocene

***内陆水域为人类提供了许多重要的服务（例如，农业用水、维持生物多样性的栖息地和娱乐场所），但这些生态系统在压力下变得脆弱。尤其是浅水湖泊，当压力稍有增加时，就会突然从清澈的状态变成浑浊的状态。然而，浅湖的突然变化并不总是被观察到，而且使这些系统容易突然变化的环境和生态条件仍然存在相当大的不确定性。******越来越多的理论和观测数据描述了压力的微小变化如何导致生态系统状态的突然转变，这被称为关键转变。然而，需要时间序列的综合分析和新的实地试验来回答一些悬而未决的问题，包括哪些因素的组合使生态系统容易受到状态突变的影响？这些非线性动力学有多普遍？通过实验和大型数据集分析的新颖混合，我将量化浅湖在不同时间尺度上对多种压力源的反应。我还将在大量室外实验池塘中确定关键转变的触发因素。这项工作建立在我以前的NSERC发现基金的基础上，在那里我的团队研究了沉积物档案，以开发温带浅湖过去生态变化的记录，并进行湖泊调查，以推进我们对这些生态系统的结构和功能的理解。******在过去的几年里，有人认为我们整个星球可能正在接近一个关键的转变。目前，要验证这些“全球临界过渡”论点的有效性是极其困难的，如果不是不可能的话，因为这些变化如何在较小的、可处理的生态系统（如浅湖）中运作仍然存在问题。我的研究旨在阐明温带浅湖是如何应对过去200年来人类活动带来的加速变化的，并为保护重点和行动提供信息。如果我们对这些问题的认识没有实质性的进步，我们将仍然对环境的突然变化及其后果毫无准备。********

***Inland waters provide humanity with numerous important services (e.g., waters for agriculture, habitats for sustaining biodiversity and sites for recreation) but these ecosystems become vulnerable to change under pressure. Shallow lakes, in particular, can change abruptly from a clear-water state to a turbid state when exposed to minor increases in stress. Yet, abrupt changes in shallow lakes are not always observed and considerable uncertainty remains about the environmental and ecological conditions that render these systems susceptible to changing suddenly.******There is a growing body of theory and observational data describing how minor changes in stress cause sudden ecosystem state shifts, which are referred to as critical transitions. However, synthetic analyses of time series and new field experiments are needed to answer lingering questions, including which combination of factors make ecosystems vulnerable to abrupt changes in state? and, how common are these nonlinear dynamics? Through a novel blend of experiments and analyses of large datasets, I will quantify how shallow lakes have responded to multiple stressors over different time scales. I will also identify triggers of critical transitions in a large array of outdoor experimental ponds. This work builds upon my previous NSERC Discovery grant, where my team studied sediment archives to develop records of past ecological changes in temperate shallow lakes and conducted lake surveys to advance our understanding of the structure and functioning of these ecosystems.******In the past few years, it has been argued that our entire planet may be approaching a critical transition. It is currently extremely difficult, if not impossible, to test the validity of these "global critical transition" arguments given that there are still questions about how such changes operate in smaller, tractable ecosystems like shallow lakes. My research is designed to elucidate how temperate shallow lakes have responded to the accelerating rate of change introduced by human activities over the past ~200 years and to inform conservation priorities and actions. Without serious advancement in our knowledge of these issues, we will remain unprepared for sudden changes in our environment and their consequences.********