Effects of climate and land use on prairie lake ecosystems

盐湖遍布各大洲，几乎占地球内陆地表积水总量的一半。盐湖也是加拿大大草原的常见特征，目前的气候模型预测，草原将变得更加干燥，这应该会导致盐碱度进一步上升。盐度对水生群落的影响是物种特有的，取决于有机体应对日益增加的渗透胁迫的能力，但总体生物多样性和物种丰富度随着盐度的降低而减少。一般来说，从鱼类到浮游动物再到大型无脊椎动物，生物群对盐度的耐受性都会增加，因此，随着盐度的变化，能量途径和食物网组成将发生戏剧性的变化。虽然已经描述了物种组成的变化，但因果关系和能量途径仍然未知。此外，为了更好地了解人类和环境对未来水质和可获得性的影响，有必要对盐湖进行更多的研究。在对20个盐度从淡水到高盐度的草原湖泊进行多年调查期间，将使用传统的湖泊学方法来表征非生物环境以及滨海和远洋群落。稳定同位素方法将用于确定沿海和远洋的能源来源、营养途径和生产力模式。这种结合的方法将使我能够1)阐明鱼类、浮游生物和沿海组成的变化将如何影响淡水湖和咸水湖的能量流动和整体生产力，2)量化沿海补贴对湖泊中上层群落的相对重要性，以及3)确定哪些环境参数对这些过程影响最大。一旦食物网模式建立，我将预测食物网组成和生产力的变化，因为由于气候变化情景预测的气候更加干燥，草原上的湖泊盐度增加。由于盐度引起的食物网组成的变化在低盐度系统中最为明显，这些系统约占草原上所有湖泊的一半，因此气候变化对湖泊生态系统的影响在草原湖泊中应该比其他地方更快地被发现。

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.