Climate control of aquatic microbial ecosystems

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Global climate projections (including those presented in the 2018 IPCC Special Report) indicate that the greatest warming effects of greenhouse gas accumulation in the atmosphere will be at high northern latitudes, and consistent with these projections, the Arctic is warming at rates 2-3 times faster than the global mean. Our NSERC Discovery program is focused on aquatic ecosystems in the changing northern environment, specifically the interactions between physical aspects such as temperature, ice cover, light and mixing, and the structure and activity of microscopic communities that underpin the food webs in high-latitude lakes and rivers. Lakes and rivers are major features of northern landscapes that in many areas are now experiencing massive change as a result of permafrost thaw and erosion. We will investigate aquatic ecosystems at the southern margin of permafrost to examine how subarctic lakes and rivers respond to ongoing landscape thaw and associated organic carbon mobilisation, with emphasis on the production of greenhouse gases (methane and carbon dioxide) and microbial community structure. Additionally, by way of isolations and culture experiments, we will evaluate the hypotheses that thaw lakes contain distinct cyanobacterial communities that are responsive to warming and that include toxic species. We will build on our limnological studies and related climate observations based out of Ward Hunt Island near the northern limit of Canada (lat. 83.1°N). Our ongoing research at this site for >15 years means that we have been present to observe extreme events and abrupt changes in ecosystem processes, and can place our studies each summer in a longer term interannual context. This work will include high-resolution observations of oxygen dynamics in a coastal lake to test the hypothesis that ecosystem metabolism is controlled by summer snow and ice conditions, in turn linked to changes in Arctic Ocean sea ice. Thick biofilm communities (microbial mats) coat the base of many lake, pond and stream ecosystems in the polar regions, and recent observations suggest that they acquire carbon and energy in more diverse ways than previously thought. We aim to apply a suite of physiological and molecular approaches in experiments to determine the functional organization of mat communities and their responses to temperature and winter darkness. The information will improve our ability to monitor, understand and predict the responses of these ecosystems to ongoing climate change. Our research directly addresses Canada's environmental needs and responsibilities in polar research and reporting, and the results are likely to continue to attract wide public, policy maker and scientific interest. The work has been entirely formulated as research training projects, resulting in advanced expertise in aquatic microbiology, ecosystem science and climate change studies to meet the growing employment opportunities in these sectors.