Effects of climate and land use on prairie lake ecosystems

所有大陆上都有咸水湖，几乎占地球内陆表面死水总量的一半。盐湖也是加拿大大草原上的一个共同特征，目前的气候模型预测，大草原将变得更加干燥，这将导致盐度进一步增加。盐度对水生群落的影响是物种特异性的，取决于生物体应对不断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降低。一般来说，从鱼类到浮游动物再到大型无脊椎动物，生物群的耐盐性都会增加，因此，随着盐度的变化，能量途径和食物网的组成也会发生巨大的变化。虽然物种组成的变化已经被描述，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用性的影响，对盐湖进行更多的研究是必不可少的。在对20个盐度从新鲜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和沿海和远洋群落。稳定同位素方法学将用于确定近海与远洋能源来源、营养途径和生产力模式。这种综合方法将使我能够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与咸水湖的能量流和整体生产力，2)量化沿海补贴对湖泊中上层生物群落的相对重要性，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起来，我将预测食物网组成和生产力的变化，因为气候变化情景预测的干旱气候会导致整个草原湖泊的盐度增加。由于盐度引起的食物网组成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在其他地方更快地被探测到。

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.