Effects of climate and land use on prairie lake ecosystems

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Saline lakes are found on all continents and account for almost half of the total volume of inland surface standing water on Earth. Saline lakes are also a common feature across the Canadian prairies, and current climate models predict that prairies will get drier, which should result in further increasing salinities. The effects of salinity on aquatic communities are species-specific and depend on the capability of an organism to cope with increasing osmotic stress, but overall biodiversity and species richness decrease with salinity. Generally, salinity tolerance for biota increases from fish to zooplankton to macroinvertebrates and, accordingly, dramatic shifts in energy pathways and food web compositions will occur as salinity changes. While shifts in species composition have been described, causal relationships and energy pathways remain unknown. Also, to better understand the consequences of human and environmental impacts on future water quality and availability, more research on saline lakes is essential. During a multi-year survey of 20 prairie lakes with salinities ranging from fresh to hypersaline, traditional limnological methods will be used to characterize the abiotic environment and littoral and pelagic communites. Stable isotope methodology will be applied to identify littoral vs. pelagic energy sources, trophic pathways and productivity patterns. This combined approach will allow me 1) to elucidate how changes in fish, plankton and littoral composition will affect energy flow and overall productivity in fresh vs. saline lakes, 2) to quantify the relative importance of littoral subsidies to the pelagic communities across lakes, and 3) to identify which environmental parameters are most influential for these processes. Once food web patterns are established, I will predict changes in food web composition and productivity as salinity increases in lakes across the prairies due to a drier climate predicted by climate change scenarios. Because salinity-induced changes in food web composition are most pronounced in systems with low salinities, which represent about half of all lakes across the prairies, the effects of climate change on lake ecosystems should be detectable much faster in prairie lakes than elsewhere.