Permafrost, defined as soil or rock that remains frozen for at least two consecutive years, is a dominant feature of the Canadian landscape. Rates of permafrost thaw have accelerated in recent decades, a trend that will continue with future climate warming. The thawing of permafrost represents a major stressor on northern lakes that may negatively impact the provision of essential lake ecosystem services. Empirical evidence of long-term impacts to lake ecological and biogeochemical function is lacking, as most studies into the effects of permafrost thaw on lakes are based on short-term observations. We are using paleolimnological techniques to track permafrost landscape change in the Northwest Territories, and the resulting lake ecosystem responses, over decadal to centennial timescales. Our field sites are based in the Inuvik-Tuktoyaktuk region (ice-rich, continuous permafrost), and the Dehcho region (discontinuous permafrost).
Aquatic ecosystems globally have a long history of exposure to harmful substances originating from industrial activities. Even seemingly remote locations are under threat, as many industrial chemicals can be transported atmospherically over long distances. Lake sediments are sinks for many contaminants of interest, and consequently paleolimnology can be used to reconstruct the deposition histories of industrial pollutants. Lake sediments also archive information on changes in aquatic biota that are commonly used as ecotoxicological indicators. We are using paleolimnological techniques to study the cumulative impacts of industrial activities and climate change on long-term contaminant dynamics in lakes. Current projects are investigating the ecotoxicological impacts of arsenic contamination in Yellowknife lakes from historic gold mining operations, legacy PCB contamination of lakes near former Arctic military radar stations, and the implications of climate change for mercury cycling in Arctic and subarctic lakes. We are also working to develop new "paleo-ecotoxicological" approaches, to best harness the information preserved in lake sediments to better understand ecological responses to long-term contaminant exposure in lakes.
Urban lakes and wetlands are under threat from multiple stressors. The increase in impervious surfaces that accompanies urban development enhances the run-off of pollutants into aquatic ecosystems. Increasing population density and boating traffic can also promote the spread of aquatic invasive species. These stressors can make urban (or urbanizing) waterbodies less resilient to climate change, which often acts as a "threat multiplier". We are studying sediment cores from southern Ontario lakes and wetlands along a gradient of urbanization and land-use activities, in order to understand how multiple stressors influence ecological resilience and trajectories of long-term ecological change. Current research projects focus on Lake Ontario coastal wetlands, and the Kawartha Lakes.
In the Dehcho region (Northwest Territories), "drunken forests" are a sign of thawing permafrost. The conversion of forests into wetlands alters the transport of organic carbon and mercury to lake ecosystems. We are studying this phenomenon at the Scotty Creek Research Station.
Giant Mine, a gold mine in Yellowknife, Northwest Territories that operated from 1948-2004 (Photo credit: L. Kimpe)
Collecting a sediment core from a Lake Ontario coastal wetland in Pickering, Ontario. Much of southern Ontario's original coastal wetlands have been lost, and those that remain have been degraded as a result of land-use pressures.