Paleoenvironmental investigation of an emerging stressor to Canadian salmon rivers

长期的观点有助于区分自然生态系统的变异性和人类的影响，并认识到环境变化的速度和幅度。古湖泊学是一门利用保存在沉积物记录中的物理、化学和生物信息来追踪长期（通常是几十年到几千年）环境变化的科学。我的研究项目结合了古湖泊学方法和现代生态采样，以更好地了解淡水生态系统如何应对自然过程和人为造成的压力。这种跨学科的方法可以作为一种强大的工具来确定因果关系，建立基线生态系统条件，并在人类活动的影响下设定现实的恢复目标。我提出的研究计划旨在了解底栖藻类Didymosphenia geminata （Didymo）在加拿大西部（不列颠哥伦比亚省温哥华岛）和东部（QC的Gaspe地区和NB北部）地区的偏远原始鲑鱼河流中滋扰生长（开花）的原因和影响。通过研究保存在沉积物记录中的信息，我们将能够评估导致藻华在这些生态系统中形成和扩散的长期环境驱动因素。这种时间视角将使我们能够确定气候变化、全球大气污染中的营养物质或历史上的土地利用实践是否正在影响Didymo水华发生的淡水。这些广泛存在的压力源被认为创造了有利于水华形成和持续的条件，尽管迄今为止还没有进行详细的评估。我们的方法可以识别最近的Didymo开花是在过去2000年里前所未有的，还是在遥远的过去发生过。我们还将通过无脊椎动物、藻类和幼年大西洋鲑鱼的采样，对加拿大东部两条河流的河流栖息地进行现代生态研究。这种方法将帮助我们了解Didymo藻华如何影响河流栖息地，并最终影响幼年鲑鱼的饮食。在有Didymo花和没有Didymo花的地点，我们将调查食物网结构和幼鲑鱼消耗的猎物数量和质量的差异。对Didymo藻华的原因和影响有了更深入的了解，将为政府和生态系统管理者提供科学知识，以帮助管理这些标志性的加拿大鲑鱼河流，这些河流最近经历了底栖藻类的大量繁殖。

A long-term perspective is useful to distinguish natural ecosystem variability from human impacts, and to recognize the rates and magnitude of environmental change. Paleolimnology is the science that uses the physical, chemical, and biological information preserved in sediment records to track environmental changes over long periods of time, often decades to millennia. My research program combines a paleolimnological approach and modern ecological sampling to better understand how freshwater ecosystems respond to natural processes and human-caused stressors. This interdisciplinary approach can be a powerful tool to determine cause-and-effect, establish baseline ecosystem conditions, and set realistic recovery goals following the impacts from human activities. My proposed research program aims to understand the causes and effects of nuisance growths (blooms) of the bottom-dwelling alga, Didymosphenia geminata (Didymo), in remote, pristine salmon rivers in western (Vancouver Island, BC) and eastern (Gaspe region of QC and northern NB) regions of Canada. By studying the information preserved in sediment records within regions currently experiencing nuisance Didymo blooms we will be able to assess the long-term environmental drivers that cause blooms to form and proliferate across these ecosystems. This temporal perspective will allow us to determine whether climatic change, nutrients from global atmospheric pollution, or historic land-use practices are impacting freshwaters where Didymo blooms occur. These widespread stressors are believed to create conditions favorable to bloom formation and persistence, although detailed evaluations have not occurred to date. Our approach can recognize whether recent Didymo blooms are unprecedented over the last ~2000 years or whether blooms have occurred in the distant past. We will also conduct a modern ecological study of river habitats in two eastern Canadian rivers by sampling invertebrates, algae, and juvenile Atlantic salmon. This approach will help us to understand how Didymo blooms affect river habitat and ultimately impact the diet of juvenile salmon. At sites with and without Didymo blooms, we will investigate differences in food web structure and the quantity and quality of prey that juvenile salmon consume. A greater understanding of both the causes and effects of Didymo blooms will provide government and ecosystem managers with scientific knowledge to aid in the management of these iconic Canadian salmon rivers experiencing recent benthic algal blooms.