STREAM SYNCHRONY: UNDERSTANDING THE SYNCHRONY OF NUTRIENTS, POLLUTION, AND WATER IN RIVER ECOSYSTEMS

河流将从自然环境中吸收的水、营养物质和污染物输送和转化。高浓度的氮和磷等营养物可能作为污染物，通过富营养化等过程破坏淡水和河口生态系统。包括农业和化肥施用在内的人为活动是许多河流系统中氮和磷污染水平的主要原因，导致英国许多地区的河流整体健康状况不佳（the Rivers Trust, 2021）。溶解有机碳（DOC）是景观碳循环的重要组成部分，同时也是河流水质的另一种潜在污染物。河网可获得的碳及其循环方式也因土地利用和气候变化而改变。英国水流中DOC的主要来源是土壤和泥炭地（例如，Ritson等人，2019），但众所周知，污水处理厂输入等人类活动也起着重要作用（Worrall等人，2019）。有趣的是，这些营养物质和污染物的输入并不是随时间而恒定的，而是随着来源的峰值供应和自然反应过程的去除而变化。此外，营养物和污染物对河流系统的潜在影响从根本上取决于河流系统输送的水量，由于降水和蒸散的季节性，这些水量可能会随季节而变化。此外，在不断变化的气候和人为压力下，所有这些输入的频率、幅度和时间都在发生变化，导致生态系统本身和水管理者都必须适应的营养和污染动态变化。理解所涉及的过程以及如何更好地管理这些过程的基本和大规模知识差距围绕着所有这些投入（水、营养物质、污染物）彼此之间的同步程度（Abbott等人，2017）。这个项目将是第一个使用现有的大型数据集来估计整个英国和欧洲的水、碳、氮和磷输入的同步（或非同步）程度，以及这种同步可能在时间和空间上如何以及为什么会发生变化的项目。帮助回答这个同步问题将提供对河流生态系统功能的更深入的见解，并为污染和水管理的优先事项提供模板

Rivers convey and transform the water, nutrients and pollutants they receive fromthe landscape. High concentrations of nutrients such as nitrogen and phosphorus may act as pollutants, damaging freshwater and estuary ecosystems through processes such as eutrophication. Anthropogenic activities, including agriculture and fertiliser application, are the main causes of polluting levels of nitrogen and phosphorus in many river systems, leading to overall poor river health across many regions of the UK (The Rivers Trust, 2021). Dissolved organic carbon (DOC) is an important component of landscape carbon cycling, and at the same time another potential pollutant of river water quality. The carbon available to river networks, and how it is cycled, has also been altered by land use and climate change. The main source of DOC to stream water in the UK are from soils and peatlands (e.g., Ritson et al., 2019), but human activity like sewage treatment plant inputs is known to also play an important role (Worrall et al., 2019). Interestingly, the input of these nutrients and pollutants is not constant over time but varies with changes in peak supply from sources and removal by natural reaction processes. Furthermore, the potential impact of nutrients and pollutants on river systems fundamentally depends on how much water river systems are conveying, which can vary seasonally due to the seasonality of precipitation and evapotranspiration. Moreover, under changing climates and anthropogenic stress, the frequency, magnitude, and timing of all these inputs are shifting, leading to changing nutrient and pollution dynamics that both ecosystems themselves and water managers have to adapt to.A fundamental and large-scale knowledge gap for both understanding the processes involved and how they could be better managed revolves around the question of how synchronous all these inputs (water, nutrients, pollutants) are with one another (Abbott et al., 2017). This project will be the first to use existing large datasets to estimate how synchronous (or asynchronous) the inputs of water, carbon, nitrogen, and phosphorus are across the UK and Europe, and how and why this synchrony might be changing in both time and space. Helping to answer this question of synchrony will provide deeper insights into the functioning of river ecosystems, and a template for priorities in pollution and water management