Grant: Discovery Grants Program - Individual

Inland waters are estimated to collectively contribute ~53% to the total global methane emissions from natural and anthropogenic sources, but these estimates are heavily based on research in dilute boreal and temperate lakes. There is much less research on solute-rich hard-water systems, despite the fact that saline and subsaline waterbodies cover half of the worlds lake volume, and may emit much less CH4 than freshwaters. Generally, my research program seeks to identify and quantify ecosystem services of understudied and undervalued hard-water aquatic ecosystems in the northern Great Plains (NGP). For this DG, I specifically aim to quantify and understand the nature of feedbacks between climate and land-use changes on CH4 emissions. Methane is responsible for the majority of aquatic CO2-equivalent flux, yet is the least well constrained GHG in terms of spatial and temporal variability, and mechanistic understanding of underlying regulatory processes. This is particularly true in the NGP, where many lakes and reservoirs have elevated sulfate concentrations that reduce methanogenesis. These primarily closed-basin aquatic ecosystems experience dramatic water level changes both naturally from variable precipitation, and owing to increasing drainage and irrigation projects across the region. These changes impact water and salt balances, organic matter composition, lake morphology and mixing regimes, and subsequently net methane production and emission. Presently, it is unknown how future climate variability and land-use changes may alter these GHG controls. This research program will address the following three objectives: 1) Quantify current diffusive, ebullitive, and plant-mediated CH4 emissions from lakes and reservoirs in the NGP; 2) Determine the impact of changing solute concentrations on CH4 emissions; and, 3) Evaluate how changes in water level affect CH4 emissions. These research objectives will be addressed through a combination of a broad 100-lake survey, seasonal sampling of a subset of 10 lakes over all 5 years with anticipated variations in water level, in situ mesocosm experiments with altered salt concentrations, and focused ebullition and plant-mediated flux measurements. Together, the results from these objectives will allow us to predict how future climate and land-use changes will alter methane emissions from prairie water bodies via alterations in salinity, water depth, and mixing regimes. Current estimates of inland water CH4 emissions are likely vastly overestimated, as they do not adequately account for solute-rich water bodies. Given that methane has a global warming potential ~38x that of CO2 over a 100-year time frame, and that climate change is altering key control mechanisms of CH4 production, it is crucial that we understand how these factors affect net GHG emissions. This research will contribute to the improvement of Canada's National Inventory Report for GHG and IPCC accounting.