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

畜牧业是英国淡水有机污染物的主要养殖类型和污染源，1000万公顷的草地上有超过965万头牛和3270万只羊，占英国全部农田的57%。当牲畜排泄物中的有机物质被冲到水中时，它会促使它们的物理、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浑浊度(因而光穿透性)、电导率、底栖底物特征和氧气状况、农用化学品的输送，包括抗微生物(抗菌、抗真菌、抗寄生虫和驱虫剂)以及天然和源自兽药使用的激素化合物，所有这些都可能在接收水域造成生态毒理影响。它们还含有营养丰富的溶解和颗粒有机物，可能会对淡水生态系统的富营养化造成影响，同时也对提取供人类消费的水域构成重大挑战。包括细菌和病毒在内的病原体增加了这一应激源组合，给畜牧业地区的娱乐用水、渔业和贝类渔业带来了持续的问题。这些应激源可能存在于大多数牲畜排泄物中，但不同的生产系统和粪便处理方法在将其转移到淡水之前在多大程度上消除或减少了它们的浓度，人们对此知之甚少。我们也不了解接收水体的环境特征对这些生态毒理和营养丰富影响以及病原体持久性的影响。气候变化导致的水温升高和水流状况的改变可能会加速这种材料的生物处理，而英国预测的降雨事件频率增加可能会超过农场的储存能力，扰乱减少牲畜对淡水影响的努力。因此，迫切需要了解这些压力源、环境和管理之间的相互作用，以推动英国淡水质量的变化。QUANTUM将解决这一巨大的知识差距，使我们能够更好地理解畜牧业是威尔士、苏格兰和北爱尔兰以及整个英格兰北部和西部以牲畜为主的集水区改变英国淡水质量的关键驱动力。这一新知识将帮助我们创建模型，能够更好地预测英国淡水质量在这些多重压力源存在的情况下如何发挥作用，以及未来它可能如何变化以应对气候变化和缓解努力。我们将通过以下方式实现这一点：1.发展关于牲畜排泄物的组成的证据，这种变化如何随粪便处理和管理而变化，以及它们在淡水中的化学和微生物持久性，这将提供一个新的框架来定义和确定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一应激源组合，使我们能够对英国各地牲畜管理实践可能的生态系统反应进行预测性理解。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应激源如何相互作用和环境特征，这对于我们了解这些淡水群落在当前缓解和气候变化的条件下如何聚集、发挥作用和应对不断变化的畜牧业做法是至关重要的。确定可能对淡水化学和生态系统产生尽可能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，以将环境和变化气候下畜牧业对英国淡水的影响降至最低。

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.