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

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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.