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，并支持重要的生物多样性。湖泊含有地球上约87%的液态地表淡水，但数量有限，质量受到人类活动的压力，气候变化加剧了这一压力。气候变化对湖泊的一些最普遍和最令人担忧的后果是湖温上升的直接和间接影响，近年来有报道称，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都有所增加，气候模型表明，在21世纪，热浪将变得更加频繁和严重。研究还表明，海洋中出现了热浪，这些热浪已被证明对世界各地的海洋生态系统产生了负面影响(例如，导致大规模珊瑚漂白)。相比之下，我们对湖泊中的极端温度如何在时间上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是非常重要的，因为极端温度对水生生态系统有很大的影响。对湖泊生态系统的破坏首先可能来自更极端、更频繁或更持久的湖泊温度(例如，在关键时间内超过某些物种的热耐力极限)。以前的研究甚至表明，大气热浪会导致湖泊中有害的蓝藻水华的发展，这是导致水质问题的一些主要原因之一，并对牛、宠物和人类的健康构成严重威胁。然而，全球范围内气候变化对湖泊极端温度的影响尚未得到研究。在此期间，我将建立一个新的和必要的湖泊研究分支学科，探索湖泊热浪的发生和后果，在本项目中首次定义为湖表面温度异常高的长期。在这项研究中，我将使用从1991年至今的大约1000个湖泊的全球独特的卫星获取的湖泊表面水温数据来研究世界各地的湖泊热浪。在三种排放情景(低、中、高)下，由1861-2099年最先进的气候模型预测驱动的数字湖泊模型也将用于研究湖泊热波在过去一个世纪中的变化，以及它们将如何对预测的未来气候变化做出反应。还将调查湖泊热浪的全球驱动因素，包括详细分析湖泊上空气象的影响，湖泊深度和表面积等局部因素，以及湖泊冰盖和水位的影响，在我们变暖的世界中，这两者都在迅速变化。最后，我将调查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华的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具有重大影响。

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.