Extreme Events in Lake Ecosystems

淡水是我们最宝贵的资源之一，为饮用水、农业和内陆渔业提供水源，并支持重要的生物多样性。湖泊含有地球上约87%的液态表面淡水，但数量有限，质量受到人类活动的压力，气候变化加剧了这种压力。气候变化对湖泊造成的一些最普遍和最令人担忧的后果是湖泊温度上升的直接和间接影响，近年来有报告称，这是全球变暖的结果。在全球气温上升的同时，研究还表明，热浪等极端事件的频率和严重程度也在增加，气候模型表明，这些事件在世纪将变得更加频繁和严重。研究还表明，海洋中会出现热浪，这已被证明对全世界的海洋生态系统产生负面影响（例如，导致大规模珊瑚白化）。相比之下，我们对湖泊中的极端温度如何及时展开以及相关的影响知之甚少。了解湖泊中极端温度的发生，在本奖学金中被称为“湖泊热浪”，是非常重要的，因为水生生态系统受到极端温度的强烈影响。对湖泊生态系统的破坏首先可能来自更极端、更频繁或寿命更长的湖泊温度（例如，某些物种的热耐受极限在临界持续时间内被超过）。以前的研究甚至表明，大气热浪可能导致湖泊中有害的蓝藻水华的发展，这是水质差问题的主要原因之一，对牛，宠物和人类构成严重的健康威胁。然而，气候变化对全球湖泊热极端事件的影响尚未得到研究。 在这个奖学金期间，我将建立一个新颖而必要的湖泊研究子学科，探索湖泊热浪的发生和后果，在这个项目中首次定义为长时间的高湖面温度。在这个奖学金，我将使用全球唯一的卫星从大约1000个湖泊从1991年到现在的湖泊表面水温数据，调查世界各地的湖泊热浪。数值湖泊模型，从1861年至2099年在三种排放情景（低，中，高）的最先进的气候模型预测驱动，也将被用来调查如何湖泊热浪在过去的世纪变化，以及他们将如何应对预测未来的气候变化。还将调查湖泊热浪的全球驱动因素，包括详细分析湖上气象的影响，湖泊深度和表面积等当地因素，以及湖泊冰盖和水位的影响，这两者都在我们变暖的世界中迅速变化。最后，我将研究湖泊热浪的生态后果，包括详细分析湖泊极端温度对湖泊藻类水华发生和严重程度的影响，以及大量鱼类死亡的增加，这对包括人类在内的许多物种所依赖的生态系统服务和栖息地资源产生重大影响。

Freshwater is one of our most valuable resources, providing water for drinking, agriculture, and inland fisheries, as well as supporting important biodiversity. Lakes contain approximately 87% of the liquid surface freshwater on earth, yet the quantity is limited and the quality under pressure from anthropogenic activities, exacerbated by climate change. Some of the most pervasive and concerning consequences of climate change on lakes are the direct and indirect effects of rising lake temperature, which has been reported in recent years as a result of global warming. Parallel to the increase in global air temperatures, studies have also shown an increase in the frequency and severity of extreme events, such as heatwaves, with climate models indicating that they will become more frequent and severe during the 21st century. Studies have also shown the occurrence of heatwaves in the oceans, and these have been demonstrated to have negative impacts on marine ecosystems worldwide (e.g., leading to mass coral bleaching). In comparison, we know very little about how thermal extremes in lakes unfold in time and what the associated impacts are. Understanding the occurrence of thermal extremes in lakes, introduced in this fellowship as 'lake heatwaves', is very important as aquatic ecosystems are strongly impacted by temperature extremes. The damage to lake ecosystems will first likely arise from lake temperatures that are either more extreme, more frequent, or more long-lived (e.g., the thermal tolerance limit of some species being exceeded for a critical duration). Previous studies have even demonstrated that atmospheric heatwaves can result in the development of harmful cyanobacterial blooms in lakes, which rank among some of the main causes of poor water quality issues, and are a serious health threat for cattle, pets, and humans. However, the influence of climate change on lake thermal extremes worldwide has not yet been studied. During this fellowship, I will establish a novel and necessary sub-discipline of lake research, which explores the occurrence and consequences of lake heatwaves, defined for the first time in this project as prolonged periods of anomalously high lake surface temperatures. In this fellowship, I will use globally unique satellite-derived lake surface water temperature data from approximately 1000 lakes from 1991-present to investigate lake heatwaves worldwide. Numerical lake models, driven by state-of-the-art climate model projections from 1861-2099 under three emissions scenarios (low, medium, high), will also be used to investigate how lake heatwaves have changed over the past century and how they will respond to projected future climatic variations. The global drivers of lake heatwaves will also be investigated, including a detailed analysis of the influence of over-lake meteorology, local factors such as lake depth and surface area, as well as the influence of lake ice-cover and water level, both of which are changing rapidly in our warming world. Finally, I will investigate the ecological consequences of lake heatwaves, including a detailed analysis of the influence of lake thermal extremes on the occurrence and severity of algal blooms in lakes and an increase in mass fish die-offs, which have large implications for the ecosystem services and habitat resources upon which many species, including humans, depend.