Long-term perspectives on aquatic ecosystem change with thawing permafrost

全球约25%的湖泊位于多年冻土区，这些湖泊是最容易受到气候变暖影响的湖泊之一，因为永久冻土融化速度加快。需要从长远的角度了解湖泊生态系统如何应对永冻土退化，以便将最近的变化放在自然生态系统变异性的背景下考虑。我的研究将使用湖泊沉积岩芯来重建湖泊历史(百年到千年的时间尺度)，以解决我们在理解湖泊生态系统对永久冻土融化引起的变革性景观变化的反应方面的关键知识空白。我将探索在加拿大西北地区永久冻土融化的两种截然不同的情景下，水生生态系统的长期变化。第一种情况集中在永久冻土南端(海河附近)的湖泊，在那里，永久冻土融化导致森林覆盖的永久冻土支撑的泥炭高原转变为湿地。这些景观变化改变了陆地碳向湖泊的流失，这对碳和污染物的循环以及水生生物群之间的生态相互作用具有重要意义。第二个场景考察了一种壮观的永久冻土退化形式，即在地面冰含量较高的地区，如新界州因努维克附近的湖泊海岸线上形成的退行性融化塌陷。融化的塌陷发展释放了大量的无机物(如粘土颗粒)到湖泊中，从水柱中清除有机碳和营养物质，增加了水的清晰度。融化后水体透明度的增加可能会增加水生生物群暴露在有害紫外线辐射下的风险，这是受衰退影响的湖泊中的一个潜在压力来源，尚未得到彻底调查。在两种永久冻土融化情景下，对千年时间尺度上的湖泊历史的研究，将使我能够重建过去暖期的生态系统状况，作为评估最近人类导致的气候变暖下的当前状况的参考框架。北方拥有丰富的淡水资源，永久冻土融化将继续加剧对这些生态系统的压力。通过研究湖泊在不同时间和空间尺度上对这种压力的反应，我的研究将为未来气候变暖下水生食物网的命运提供洞察力，有助于保护加拿大北部健康和多样化的水生生态系统。

Approximately 25% of all lakes globally are located in permafrost regions, and these lakes are among the most vulnerable to climate warming through accelerated rates of permafrost thaw. A long-term perspective is needed to understand how lake ecosystems are responding to permafrost degradation, in order to place recent changes in the context of natural ecosystem variability. My research will use lake sediment cores to reconstruct lake histories (centennial to millennial timescales), in order to address key knowledge gaps in our understanding of the responses of lake ecosystems to the transformative landscape changes occurring as a result of permafrost thaw. I will explore long-term aquatic ecosystem changes under two contrasting scenarios of thawing permafrost in Canada's Northwest Territories. The first scenario focuses on lakes at the southern limit of permafrost (near Hay River), where thawing permafrost leads to the conversion of forested permafrost-supported peat plateaus into wetlands. These landscape changes alter terrestrial carbon run-off to lakes, which has implications for carbon and contaminant cycling, and ecological interactions among aquatic biota. The second scenario examines a spectacular form of permafrost degradation, retrogressive thaw slumps that form on the shorelines of lakes in areas of high ground-ice content, such as near Inuvik, NT. Thaw slump development releases large amounts of inorganic material (such as clay particles) to lakes, which scavenges organic carbon and nutrients out of the water column, and increases water clarity. The increase in water clarity following thaw slumping may increase the exposure of aquatic biota to harmful UV radiation, a potential stressor in slump-impacted lakes that has yet to be thoroughly investigated. The study of lake histories on millennial timescales, under both permafrost thaw scenarios, will allow me to reconstruct ecosystem conditions during past warm periods as a frame of reference from which to evaluate current conditions under recent human-induced climate warming. The north hosts an abundance of freshwater resources, and permafrost thaw will continue to intensify as a stressor on these ecosystems. By examining lake responses to this stressor over varying temporal and spatial scales, my research will provide insights into the fate of aquatic food webs under future climate warming, contributing to the protection of healthy and diverse aquatic ecosystems in northern Canada.