Bridging local processes and broad-scale patterns in aquatic biogeochemistry under rapid environmental changes

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Aquatic ecosystems are biogeochemical hotspots in a complex landscape that undergoes rapid natural and human-driven changes in land-use, land-cover, hydrology, and climate. The pathways by which these changes affect aquatic ecosystem functioning, however, remain poorly understood due to the scale disconnect that limits knowledge transfer between local, process-based studies and broad-scale, pattern-based studies in aquatic biogeochemistry. Conducting research at the interface of landscape ecology and aquatic biogeochemistry, I propose to develop scaling principles that will allow to bridge local processes and broad-scale patterns in aquatic carbon and nutrient cycling. The main focus is on the coupling between ecological and biogeochemical processes along common environmental gradients that dictate the temporal and spatial patterns in aquatic dissolved organic matter (DOM), a master variable with direct and indirect influence on virtually every process occurring in the water column of lakes and rivers. The main objectives of the program are to: 1) determine the effects of changing DOM stoichiometry on aquatic biogeochemistry across temporal hydrological gradients, 2) assess the scalability of hydrological patterns across spatial landscape gradients and 3) compare the effects of climate, land cover and land use on DOM patterns at continental scale. Relying on the fast-growing development of analytical methods, collaboration networks, modeling capacity and automated sensors, my program will combine a temporal and a spatial field work components around the Université de Montréal field station facilities in the Laurentians region, Québec, with the analysis of existing limnological and geographical data assembled for over 50 000 lakes across the NE US, Ontario and Québec. This program represents a crucial step toward disentangling the pathways through which rapid changes in climate and land-use drive the fate of terrestrial carbon and nutrients in continental watersheds. This understanding, in turn, will allow scientists and managers to better forecast the response of lakes and rivers to complex and interacting changes in climate, land-cover, land-use and hydrology, and thus to target the most pressing issues for landscape management from local to continental scales.