Aquatic community analyses of southeastern Canadian lakes: integrating environmental DNA and paleolimnological approaches

我们很幸运，加拿大拥有丰富的内陆水域，从中我们获得了许多基本的生态系统服务（例如，饮用水和食物）。然而，在全球范围内，一系列环境压力因素（如气候变化、入侵物种和污染）的强度正在增加，而它们对加拿大水生生态系统和群落的影响却知之甚少。湖泊是研究压力源在何时、何地以及如何单独或联合作用改变水生群落的理想系统。由于湖泊位于洼地中，它们自然地整合了整个流域和大气区的变化，这些信号随后被保存在湖泊沉积物岩心中。最近对加拿大内陆水研究的回顾发现了许多差距和研究机会。由于加拿大的大多数湖泊研究都采用了有限的地理方法，我们无法对为什么一些湖泊或地区对一系列压力源比其他地区更敏感产生一个清晰的观点。我的计划将解决这一差距，并推进新兴的环境DNA研究（eDNA；在散装水，沉积物或土壤样本中发现的遗传物质的分析，而不必首先分离分类群）。我的研究项目将询问水生群落的分布和动态如何与分布在加拿大四个生态区的一套湖泊的地貌因素、环境压力因素和生物相互作用有关。回答这个问题将提供基本的知识，了解在没有强烈的人类压力的情况下湖泊群落的结构，并深入了解这些生态系统自工业革命（~1880年）以来的变化。我们将首先通过分析45个湖泊的沉积物岩心来研究浮游动物组合在过去200年里是如何变化的；我们的工作将补充早期的多样性研究，但提供更强大的时空框架。我的团队还将领导一个多步骤的eDNA项目，以清楚地确定这种方法的优势和局限性。首先，我们将进行研究，以量化eDNA结果与传统方法在季节尺度和整个景观中枚举生物体的相关性。然后，我们将应用eDNA方法研究沉积物岩心中水生食物网的动态，我们将分析亚化石浮游动物的岩心。eDNA方法有可能让我们解决更广泛的食物网发生变化的方式和原因。总的来说，我的长期研究目标是推进我们对湖泊结构和功能的理解，并量化这些生态系统如何应对工业革命以来人类活动带来的加速变化。通过这个项目，我的学员和我将塑造eDNA研究领域，并确定敏感的湖泊特征以及带来湖泊社区最大变化的压力源，这将为湖泊和流域管理提供信息。

We are fortunate in Canada to have an abundance of inland waters from which we draw numerous essential ecosystem services (e.g., drinking water & food). Yet, a portfolio of environmental stressors is increasing in intensity globally (e.g., climate change, invasive species & pollution), and their impacts on Canadian aquatic ecosystems and communities are poorly understood. Lakes represent ideal systems to study when, where, and how stressors have acted alone or in combination to alter aquatic communities. Since lakes are situated in depressions, they naturally integrate changes throughout their watersheds and airsheds, and these signals are then preserved in lake sediment cores. Recent reviews of Canadian inland water research have identified many gaps and research opportunities. As most lake research in Canada has taken a limited geographic approach, we have not been able to generate a clear perspective on why some lakes or regions are more sensitive to a suite of stressors over others. My program will address this gap as well as advance the emerging study of environmental DNA (eDNA; analysis of genetic material found within bulk water, sediment or soil samples without having to first isolate taxa). My research program will ask how aquatic community distributions and dynamics are related to geomorphic factors, environmental stressors and biotic interactions in a suite of lakes distributed across four Canadian ecozones. Answering this question will provide fundamental knowledge on what structures lake communities in the absence of intensive human pressures and yield insight into how these ecosystems have changed since the Industrial Revolution (~1880 AD). We will first examine how the zooplankton assemblages have changed over the past ~200 years by analysing sediment cores from 45 lakes; our work will complement earlier diversity studies but provide a more robust spatio-temporal framework. My team will also lead a multi-step eDNA program to clearly identify the strengths and limitations of this approach. First, we will conduct studies to quantify how strongly correlated are eDNA results to traditional methods for enumerating organisms at a seasonal scale and across the landscape. We will then apply eDNA methods to study the dynamics of aquatic food webs from sediment cores, the same cores from which we will analyse subfossil zooplankton. The eDNA approach has the potential to allow us to address how and why the broader food web has changed. Overall, my long-term research goals are to advance our understanding of the structure and functioning of lakes and to quantify how these ecosystems have responded to the accelerated rate of change introduced by human activities since the Industrial Revolution. With this program, my trainees and I will shape the field of eDNA research and identify sensitive lake features as well as stressors that bring about the largest changes in lake communities, which informs lake and watershed management going forward.