Salinization of Canadian Prairie Surface Waters: Biogeochemical impacts and Ecosystem Outcomes

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Human activities are increasing the salt content of inland aquatic networks (rivers, lakes, and reservoirs) worldwide, with complex and unclear biogeochemical implications. For example, increasing concentrations of cations and anions (e.g., sulfate) may alter the redox properties of ecosystems, the composition and functioning of food webs, and physico-chemical properties in ways that affect the bio-availability and flow of materials through continental landscapes. My long-term research program aims to understand integrated human impacts on biogeochemical processes underpinning aquatic ecosystem health and functioning. The plan presented herein is designed to uniquely support my overarching research program. Specifically, this program is designed to address salinization impacts on bio-reactive sulfur, organic matter (OM), and net greenhouse gas (GHG) production in continental aquatic ecosystems. Defining the trends of salinization and effects on aquatic biogeochemical processes is critical for biogeochemists and ecologists across Canada and throughout the world, since salinization is a potent and globally widespread problem that has myriad effects on ecosystem functioning. The proposed research will define the connection between ecosystem salinization and cycling of OM and GHGs in a model Canadian Prairie aquatic network by addressing 4 short-term objectives: 1) Quantifying relations between salinity, sulfate availability, and dimethylsulfide (DMS) cycling; 2) Elucidating effects of ionic strength and composition on methane (CH4) cycling. 3) Quantifying salinization effects on aquatic OM cycling. 4) Linking salinization changes to whole-network, multi-gas fluxes of GHGs. These objectives, applied within a model Canadian river network, will help define how salinization is changing ecosystem processes in continental landscapes. We will assemble data from new and existing sampling in the Oldman River Network, and from controlled experimentation at the Aquatic Research Facility (U. Lethbridge). This information will provide critical new insights into human impacts on contrasting elemental cycles (e.g., sulfur, carbon, nitrogen, phosphorus), an aspect of global biogeochemistry that remains poorly resolved. This research will also help define the atmospheric warming potential of integrated aquatic networks, thereby contributing to global initiatives tracking changes in atmospheric GHG content. Defining salinity impacts on OM bioavailability will provide critical insight into aquatic biogeochemical functioning, since development of OM pools is the precursor for GHG production, and a major source of nutrients supporting ecosystem productivity and carbon sequestration. Improved understanding of OM bioavailability under contrasting scenarios of salinization will have practical benefits for water quality monitoring efforts focused on abatement of eutrophication, a central issue for agriculturally dominated Northern Great Plains landscapes.