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

咸水湖遍布各大洲，几乎占地球内陆地表积水总量的一半。最近的工作已经证实，在盐湖的社区组成强烈的盐度变化，但其他物理，化学和形态特征也产生重要的影响。因此，我提出了一个湖泊调查，以量化景观格局的食物网的变化，气候和湖泊化学。在随后的封闭实验中，我将更具体地评估相对于其他关键参数，如营养物质，DOC和湖泊深度的盐度对食物网动态的独特影响。由于渗透胁迫的发生在不同的营养水平，在盐湖的食物网的复杂性是高度可变的，比淡水湖更多样化。在中等盐度下对鱼类的抑制应相继将顶部食鱼动物的关键作用转移到一系列受影响较小的无脊椎动物捕食者，并且根据其摄食模式，对浮游生物群落的影响可能差异很大。基于稳定同位素测量，我将开发混合模型，以量化元素和营养源和能量流的主要途径内的食物网（如营养级联与行会内捕食）对比捕食制度，这将推动我们的理解捕食者-猎物的相互作用超出了我们所知道的淡水系统的研究。最后，全球气候变化情景预测，加拿大平原（和世界其他地区）将在未来经历更多的干旱，因此，水资源短缺将加剧。用水做法将给许多已经紧张的水生环境，特别是已知对水文变化敏感的咸水湖，增加额外的压力。因此，更好地了解盐湖动态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.