Stuck in the mud: addressing the fine sediment conundrum with multiscale and interdisciplinary approaches to support global freshwater biodiversity

环境变化正在全球范围内发生。淡水生态系统是世界上一些最濒危的栖息地，其多样性的下降幅度（1970-2014年期间为83%）远远超过陆地生态系统。河流生态系统健康下降的主要原因之一是与过度的细沉积物沉积（通常指小于2mm的颗粒）相关的栖息地丧失。细沉积物是河流系统的自然组成部分，然而，土地利用的改变（例如集约化耕作）和渠化/蓄水（通过水坝和水库）改变了细沉积物的数量，使现在的投入远远超过历史水平。此外，与气候变化相关的水文极端事件的增加，如强降雨事件，可能会进一步增加细沉积物向河道的输送。细沉积物的沉积改变和退化了溪流的栖息地，使河流不适合动植物的生存。这种变化导致河流生态系统生物多样性的减少，并影响到食物网的所有组成部分，从鱼类和昆虫到藻类。因此，了解细沉积物的生态影响对于管理河流至关重要，这样它们才能支持和维持健康的生态系统功能，并支持人为活动（例如渔业、娱乐活动）。然而，这是具有挑战性的，因为许多环境因素控制着细沉积物对动植物的影响。拟议的研究金旨在了解和量化哪些环境因素（例如土地利用、河流内细沉积物和砾石的大小、一年中的时间）影响河流群落细沉积物沉积的严重程度。具体目标是(i)量化英国和国际上细沉积物负荷和生态响应之间的趋势；（ii）确定在生态退化发生之前是否存在细泥沙负荷的阈值，以及这在个别河流中如何变化；（iii）了解环境控制（例如粒度、水文交换）如何构成细泥沙的影响；（iv）概述未来的研究议程，以解决河流细沉积物的管理问题。为了实现这些目标，我的奖学金将提供一个框架，以确定何时以及哪种河流类型（例如高地或低地，地质）在国际上最容易受到细沉积物压力的威胁。该研究金将把重点放在大型无脊椎动物（蜗牛、昆虫和甲壳类等河流无脊椎动物）上，作为一个目标生物，它们数量丰富、种类多样，分布在全球各地。该奖学金是一个新颖而令人兴奋的研究项目，具有国际影响力和适用性，将全球数据集与多国实地和人工河道实验（高山和低地）以及不同空间尺度的实验室实验相结合，以发展和验证跨越不同环境设置的理论。该奖学金将使我们的理解发生令人兴奋的变化，并将解决独特的基础研究问题，同时与英国法定监管机构和最终用户（如英格兰环境局、威尔士自然资源局和苏格兰环境保护局）协同工作。所产生的研究将对利益相关者如何分配资源来监测和管理英国河流生态系统产生重要影响，并将使更有效和有针对性的保护和恢复计划成为可能。

Environmental change is happening on a global scale. Freshwater ecosystems represent some of the most endangered habitats in the world, with declines in diversity (83% in the period 1970-2014) far exceeding that of terrestrial counterparts. One of the primary causes of reduced riverine ecosystem health is a loss of habitat associated with excessive fine sediment deposition (typically referred to as particles <2mm). Fine sediment is a natural part of river systems, however alterations to land use (e.g. intensive farming) and channelization / impoundment (via dams and reservoirs) have altered the quantity of fine sediment such that inputs now far exceed historic levels. Additionally, increasing hydrological extremes associated with climatic change, such as intense rainfall events, are likely to further increase the delivery of fine sediment to river channels.Fine sediment deposition alters and degrades instream habitats making rivers unsuitable for flora and fauna to live in. Such changes lead to reductions in the biodiversity of riverine ecosystems and affects all components of the food web from fish and insects through to algae. Understanding the ecological implications of fine sediment is therefore imperative to be able to manage our rivers so that they can support and sustain healthy ecosystem functioning and support anthropogenic activities (e.g., fisheries, recreational activities). This is however challenging because a number of environmental factors control the consequences of fine sediment for flora and fauna. The proposed Fellowship aims to understand and quantify which environmental factors (e.g. land use, size of fine sediment and of the gravels within the river, time of year) influence the severity of fine sediment deposition for rivercommunities. Specific objectives are to (i) quantify the trends between fine sediment loading and ecological responses in the UK and internationally; (ii) determine if there is a threshold of fine sediment loading before ecological degradation occurs and how this varies within individual rivers, (iii) develop understanding of how environmental controls (e.g. grain size, hydrological exchange) structure the effects of fine sediment and; (iv) outline a future research agenda to tackle the management of fine sediment in rivers. In achieving these objectives, my Fellowship will provide a framework to determine when and which river types (e.g. highland or lowland, geology) are most at threat from fine sediment pressures internationally. The Fellowship will focus on macroinvertebrates (river invertebrates such as snails, insects and crustaceans) as a target organisms being abundant, diverse and occurring across the globe. The Fellowship represents a novel and exciting research programme with international reach and applicability that combines global datasets with multi-country field and artificial stream channel experiments (alpine and lowland) and laboratory experiments over different spatial scales to develop and validate theories spanning different environmental settings. The fellowship will lead to an exciting step-change in our understanding and will address unique fundamental research questions whilst working synergistically with UK statutory regulatory agencies and end-users such as the Environment Agency of England, Natural Resources Wales and Scottish Environmental Protection Agency. The research generated will have important ramifications for how stakeholders allocate resources to monitor and manage UK riverine ecosystems and will enable more efficient and targeted conservation and restoration plans.