Climate control of aquatic microbial ecosystems

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Global climate models predict that the greatest warming effects of greenhouse gas accumulation in the atmosphere will be at the highest latitudes of the Arctic, and consistent with these projections, the High Arctic appears to be warming at rates well above the global mean. Over the last 15 years, we have established an observatory at Ward Hunt Island, at the northern limit of the Canadian High Arctic coastline. This has proven to be a strategic research site for the detection and analysis of environmental change given the diversity of freshwater and marine ecosystems, their extreme sensitivity to perturbations of the cryosphere (snow and ice-containing environments), and the current trend of accelerated warming at this far northern latitude (83 degrees North, 1018 km north of Resolute Bay, 172 km northwest of Alert). For this next phase of my Discovery Grant program, we will focus our research on the Ward Hunt region via a coordinated set of graduate student and postdoctoral projects, to address key questions and hypotheses about aquatic habitats, communities and processes in the warming Arctic.Microscopic life underpins the biological production, food web processes, nutrient fluxes and biodiversity of polar ecosystems. Our research program will focus on achieving an improved understanding of this microbial world in the lakes, wetlands, streams and fjords along the coast of northern Ellesmere Island, within helicopter range of our base camp and laboratory at Ward Hunt Island. Three themes will be addressed, building on our studies to date. Firstly, we will apply advanced microbiological and molecular (DNA and RNA sequencing) methods to evaluate the network relationships among the microbial plankton populations in these waters, and the changes in microbial community structure and function across salinity gradients, including in newly emergent ecosystems that were previously constrained by thick ice. Secondly, we will address the striking dichotomy in the distribution of minute photosynthetic plankton (cells less than 3 micrometres in diameter, termed picophytoplankton) in which the dominant cell types are picocyanobacteria in lakes and picoeukaryotes in the sea. This research will include observations, cultures and controlled experiments to evaluate the food web effects on these populations relative to their temperature-dependent growth rates. Thirdly, we will continue our work on the thick biofilm communities that coat the base of shallow freshwaters (cyanobacterial mats) by way of culture experiments and molecular analyses to determine how these major constituents of northern ecosystems are functionally organized, the coupling between photosynthetic and non-photosynthetic constituents of the communities, and their responses to environmental change. The projects in these three themes will apply diverse approaches including emerging new molecular and cytometric methods and will address topics at the leading edge of microbial ecology. The results will improve our ability to monitor and predict the responses of northern ecosystems to ongoing environmental change.The originality of this work lies in our proven ability to achieve new insights into microbial ecosystems at this most remote and strategic part of Canada, to place this work in a broad global as well as ecological context, and to report our observations of ecosystem change in this northernmost region to Canadians (including northerners) and to the rest of the world. Our research directly addresses Canada’s environmental needs and international responsibilities in polar research and reporting, and the results are likely to continue to attract wide public, policy maker and scientific interest.