Environmental controls of food web structure and energy flow in saline lakes

盐湖遍布各大洲，几乎占地球内陆地表积水总量的一半。最近的研究证实，盐湖的群落组成随着盐度的变化而变化很大，但也表明其他物理、化学和形态计量特征也起着重要的影响。因此，我提出了一项湖泊调查，以量化食物网变化的景观模式，以响应气候和湖泊化学。在随后的围栏实验中，我将更具体地评估盐度相对于其他关键参数(如营养物质、DOC和湖泊深度)对食物网动态的独特影响。由于渗透胁迫的开始在不同的营养水平上有所不同，盐湖中食物网的复杂性与淡水湖相比具有高度的变异性和多样性。在中等盐度下对鱼类的抑制应该会将顶端浮游生物的关键作用依次转移到一系列受影响较小的无脊椎动物捕食者身上，根据它们的摄食方式，对浮游生物群落的影响可能会有很大差异。基于稳定的同位素测量，我将开发混合模型，以量化不同捕食制度下食物网内的元素和营养来源以及主要能量流动路径(例如营养级联和行内捕食)，这将推动我们对捕食者-猎物相互作用的理解，超出我们从淡水系统研究中所知的范围。最后，全球气候变化情景预测，加拿大平原(和世界其他地区)未来将经历更多干旱，因此水资源短缺将会加剧。用水做法将给许多本已紧张的水生环境增加额外的压力，特别是对已知对水文变化敏感的咸水湖。因此，更好地了解盐湖动力学将使我们能够预测这些系统未来变化的影响。

Saline lakes are found on all continents and account for almost half of the total volume of inland surface standing water on Earth. Recent work has confirmed that community composition in saline lakes strongly varies with salinity, but suggests that other physical, chemical, and morphometric characteristics exert important influences as well. Consequently, I propose a lake survey to quantify landscape patterns of food web variability in response to climate and lake chemistry. In subsequent enclosure experiments, I will more specifically evaluate the unique effects of salinity on food web dynamics relative to other key parameters, such as nutrients, DOC, and lake depth. As the onset of osmotic stress varies among trophic levels, the complexity of food webs in saline lakes is highly variable and more diverse than in freshwater lakes. The suppression of fish at moderate salinities should successively shift the crucial role of the top-planktivore to a series of less affected invertebrate predators, and depending on their feeding mode, the effects on the plankton community may vary tremendously. Based on stable isotope measurements, I will develop mixing models to quantify elemental and nutrient sources and major pathways of energy flow within food webs (e.g. trophic cascade vs. intra-guild predation) of contrasting predation regimes, which will propel our understanding of predator-prey interactions beyond what we know from studies in freshwater systems. Finally, global climate change scenarios predict that the Canadian plains (and other regions worldwide) will experience more droughts in the future, and consequently, water shortages will increase. Water-use practices will add additional strain to many already stressed aquatic environments, especially to saline lakes that are known to be sensitive to hydrologic changes. As a result, a better understanding of saline lake dynamics will allow us to forecast impacts of future changes in these systems.