Quantifying the combined nutrient enrichment, pathogenic, and ecotoxicological impacts of livestock farming on UK rivers

畜牧业是英国淡水中主要的农业类型和有机物污染来源，在1000万公顷的草地上有超过965万头牛和3270万只羊，占英国所有农业用地的57%。当牲畜排泄物中的有机物被冲入水体时，会导致水体的物理、化学和生态质量和功能发生变化。这些变化包括接收水体的浊度（以及因此产生的光穿透性）、电导率、底栖基质特性和氧体制的变化，包括抗微生物剂（抗菌、抗真菌、抗寄生虫和抗蠕虫剂）和激素化合物在内的农用化学品的输送，包括天然的和来自兽药用途的化合物，所有这些都可能对接收水体产生生态毒理学影响。它们还含有富含营养的溶解有机物和颗粒有机物，可能会对淡水生态系统产生富营养化影响，同时也对提取供人类食用的水构成重大挑战。包括细菌和病毒在内的病原体增加了这一压力源组合，对畜牧业地区的娱乐用水、渔业和贝类渔业构成了一个持久的问题。这些压力源可能存在于大多数牲畜排泄物中，但人们对不同的生产系统和粪便处理方法在将其转移到淡水之前去除或降低其浓度的程度知之甚少。我们也不了解接收水体的环境特征对这些生态毒理学和营养富集影响以及病原体持久性的影响。气候变化引起的水温升高和水流变化可能会加速这种材料的生物处理，而预计英国降雨事件的频率增加可能会压倒农场的储存能力，使减少牲畜对淡水影响的努力变得混乱。因此，迫切需要了解这些压力源、环境和管理在驱动英国淡水质量变化中的相互作用。QUANTUM将解决这一实质性的知识差距，使我们能够更好地了解畜牧业是威尔士、苏格兰和北爱尔兰以及整个英格兰北部和西部以畜牧业为主的集水区改变英国质量的关键驱动因素。这些新知识将帮助我们创建模型，更好地预测英国淡水质量在这些多重压力源存在下的功能，以及未来如何应对气候变化和缓解努力。我们将通过以下途径实现这一目标：开发牲畜排泄物组成的证据，根据粪便处理和管理，以及它们在淡水中的化学和微生物持久性如何变化，这将提供一个新的框架来定义和背景下它们对英国淡水施加的压力。探索不同的淡水生物群如何应对这些压力源组合，使我们能够对整个英国牲畜管理实践可能的生态系统反应有一个预测性的理解。3 .了解牲畜排泄物如何扰乱淡水生态系统的状态，以及这些通量中的多种压力源如何相互作用和环境特征，如果我们要了解这些淡水群落如何在当前、缓解和气候变化的条件下聚集、运作和应对不断变化的畜牧业实践，这是至关重要的。确定可能对淡水化学和生态系统产生最低影响的畜牧业生产实践和管理方法，这将为我们的项目合作伙伴制定政策和实践提供关键基础，以最大限度地减少在环境和气候变化下畜牧业对英国淡水的影响。

Livestock farming is the dominant farming type and source of organic matter pollution in UK freshwaters, with over 9.65M cattle and 32.7M sheep on 10M hectares of grassland, representing 57% of all agricultural land in the UK. When organic matter from livestock excreta is flushed to waters it drives changes in their physical, chemical and ecological quality and function. These include changes to the turbidity (and therefore light penetration), conductivity, benthic substrate character and oxygen regimes of the receiving waterbody, the delivery of agrochemicals including anti-microbial (antibacterial, antifungal, antiparasitic and antihelminth agents) and hormone compounds, both natural and derived from veterinary pharmaceutical use, all of which are likely to drive ecotoxicological impacts in receiving waters. They also contain nutrient-rich dissolved and particulate organic matter likely to drive eutrophication impacts in freshwater ecosystems, while also presenting a significant challenge for waters abstracted for human consumption. Pathogens, including bacteria and viruses, add to this portfolio of stressors, presenting a persistent problem for recreational water use, fisheries and shellfisheries in livestock farming areas. These stressors are likely to be present in most livestock excreta, but the extent to which different production systems and manure handling practices remove or reduce their concentration prior to their transfer to freshwaters is poorly understood. Nor do we understand the impact of the environmental character of the receiving waterbody on these ecotoxicological and nutrient enrichment impacts and pathogen persistence. Climate change-induced increases in water temperature and alterations in flow regime may then accelerate biological processing of this material, while the increased frequency of rainfall events predicted for the UK may overwhelm on-farm storage capacity, confounding efforts to reduce livestock impacts on freshwaters. There is thus an urgent need to understand interactions between these stressors, environment and management in driving changes in UK freshwater quality.QUANTUM will address this substantial knowledge gap, allowing us to better understand livestock farming as a key driver of changing UK quality in the livestock-dominated catchments of Wales, Scotland and Northern Ireland, and throughout the north and west of England. This new knowledge will help us create models that can better predict how UK freshwater quality functions in the presence of these multiple stressors, and how it is likely to change in future in response to climate change and mitigation efforts.We will achieve this by:1. Developing evidence on the composition of livestock excreta, how this varies according to manure handling and management, and their chemical and microbiological persistence in freshwaters, which will provide a new framework to define and contextualise pressures they exert on UK freshwaters.2. Exploring how different freshwater biota respond to this portfolio of stressors, allowing us to develop a predictive understanding of likely ecosystem responses to livestock management practices across the UK.3. Understanding how livestock excreta perturb the state of freshwater ecosystems, and how the multiple stressors in these fluxes interact with each other and environmental character, which is essential if we are to understand how these freshwater communities assemble, function and respond to changing livestock farming practices, under current, mitigated and climatically-altered conditions.4. Identifying the livestock production practices and management approaches likely to generate the lowest possible impacts on freshwater chemistry and ecosystems, which will provide critical underpinning for the developing policy and practice by our project partners, to minimise livestock farming impacts on UK freshwaters under ambient and changing climate.