Effects of multiple stressors on littoral habitat and lake ecosystems

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Lakes and rivers provide us many ecological services, from drinking water to recreation opportunities. They are also considered among the most human-impacted ecosystems on the planet. Long-term (multi-decadal or longer) environmental data, however, are rarely available as a benchmark to evaluate human-induced ecosystem changes and therefore paleoecological data are needed to assess human disturbance to aquatic ecosystems. The near-shore littoral zone of lakes is often the earliest and most severely impacted region of a lake. Because of this, it is important that we integrate the response of the ecologically influential and diverse near-shore littoral environment into our understanding of aquatic ecosystem change. In temperate lakes, one of the defining features of the near-shore littoral zone are submerged plant beds (macrophytes). Macrophyte beds are among the most biodiverse areas in lakes, are sinks for excessive nutrients, serve as important habitat for numerous animals including top predators, and enhance ecosystem resilience. Much of our understanding of how humans alter macrophyte beds comes from studies on shallow (max depth <5m), hyper-nutrient rich, lakes in Europe where macrophyte biomass has all but disappeared. Because past studies have focused primarily on these shallow, hyper-nutrient rich systems their results are not directly transferable to the deeper, stratified, and more nutrient-limited lake ecosystems common in Canada. Therefore, we require new research to advance our knowledge of human-impacts on macrophyte beds in Canadian lakes. My research will evaluate macrophyte response to common environmental stressors (climate change, land-use change, invasive species, and pollution) from the within-bed to the whole-lake scale and determine what impact, if any, changes in the macrophyte beds have on the ecological resilience of the whole-lake ecosystem. This research will advance our understanding of how human activities are altering the near-shore littoral environment and how these changes impact the entire lake ecosystem in deeper, stratified, nutrient-limited lakes common in Canada. This research will help environmental managers and lake associations better conserve and restore Canada’s freshwater resources in a changing world.