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

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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.