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最濒危的栖息地之一，其多样性下降（1970-2014年期间下降83%）远远超过陆地生态系统。河流生态系统健康状况下降的主要原因之一是与过多的细沉积物沉积（通常指小于2毫米的颗粒）有关的栖息地丧失。细颗粒沉积物是河流系统的自然组成部分，但是土地利用的改变（例如集约化农业）和渠道化/蓄水（通过水坝和水库）改变了细颗粒沉积物的数量，使得输入量现在远远超过历史水平。此外，与气候变化相关的水文极端事件不断增加，如强降雨事件，可能会进一步增加流入河道的细颗粒沉积物。细泥沙的沉积改变和退化了不稳定的生境，使河流不适合植物群和动物群生存。这种变化导致河流生态系统的生物多样性减少，并影响到从鱼类和昆虫到藻类的食物网的所有组成部分。因此，了解细泥沙的生态影响对于管理我们的河流至关重要，以便它们能够支持和维持健康的生态系统功能并支持人类活动（例如，渔业、娱乐活动）。然而，这是具有挑战性的，因为一些环境因素控制着细沉积物对植物群和动物群的影响。拟议的研究金旨在了解和量化哪些环境因素（如土地利用、河流中细沉积物和砾石的大小、一年中的时间）影响河流社区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颗粒泥沙负荷与生态响应之间的趋势;（ii）确定生态退化发生前细颗粒泥沙负荷是否存在阈值，以及这在单个河流中如何变化;（iii）了解环境控制（iv）概述未来研究议程，以解决河流细泥沙的管理问题。在实现这些目标的过程中，我的奖学金将提供一个框架，以确定哪些河流类型（如高地或低地，地质）最受国际细泥沙压力的威胁。该研究金将侧重于大型无脊椎动物（河流无脊椎动物，如蜗牛、昆虫和甲壳类动物），将其作为一种目标生物，因为它们数量丰富、种类繁多，遍布地球仪。该研究金是一个新颖和令人兴奋的研究方案，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，以开发和验证跨越不同环境背景的理论。该奖学金将导致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以监测和管理英国河流生态系统产生重要影响，并将实现更有效和更有针对性的保护和恢复计划。

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 river communities. 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 which rivers 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.