Paleoenvironmental investigation of an emerging stressor to Canadian salmon rivers

长远的观点有助于区分自然生态系统的可变性和人类的影响，并认识到环境变化的速度和程度。古湖沼学是一门利用沉积物记录中保存的物理、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沼学方法和现代生态采样，以更好地了解淡水生态系统如何对自然过程和人类造成的压力做出反应。这种跨学科的方法可以成为确定因果关系、建立基线生态系统条件以及在人类活动的影响之后设定现实的恢复目标的强大工具。我提出的研究计划旨在了解在加拿大西部(不列颠哥伦比亚省温哥华岛)和东部(昆士兰州加斯佩地区和北卡罗来纳州北部)偏远、原始的三文鱼河流中，底栖藻类Didymphenia gminata(Didymo)滋生(水华)的原因和影响。通过研究目前正在经历水华滋扰的区域内的沉积物记录中保存的信息，我们将能够评估导致水华在这些生态系统中形成和扩散的长期环境驱动因素。这一时间视角将使我们能够确定气候变化、全球大气污染的营养物质，或者历史上的土地利用做法是否正在影响发生双季水华的淡水。这些普遍存在的应激源被认为创造了有利于水华形成和持续的条件，尽管到目前为止还没有进行详细的评估。我们的方法可以识别最近的双星爆发是否是过去2000年来前所未有的，或者是否发生在遥远的过去。我们还将通过采样无脊椎动物、藻类和大西洋鲑鱼幼鱼，对加拿大东部两条河流的河流栖息地进行现代生态学研究。这一方法将帮助我们了解水华如何影响河流栖息地，并最终影响幼年鲑鱼的饮食。在有和没有水华爆发的地点，我们将调查幼年鲑鱼在食物网络结构和猎物的数量和质量上的差异。更好地了解水华的原因和影响，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三文鱼河流，经历最近的底栖藻华水华。

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.