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

点击翻译按钮获取中文摘要

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.