Characterisation of the nature, origins and ecological significance of dissolved organic matter in freshwater ecosystems

联合国已将沿海营养污染和缺氧列为当前全球环境面临的最大威胁之一。影响包括沿海水域的富营养化和氧气消耗，以及对生态系统、生物多样性和沿海水质的相关损害。联合国环境规划署马尼拉宣言（2012年1月）将海洋环境的营养物质富集确定为其《保护海洋环境免受陆源活动影响全球行动纲领》的三大重点之一，这也是2012年6月举行的bbb10 +20联合国可持续发展大会的重点之一。与此同时，《远距离越境空气污染国际公约》（CLRTAP）正在修订《哥德堡议定书》附件九（旨在减少酸化、富营养化和地面臭氧），以进一步减少陆基活动产生的氨排放。在欧洲，为了实现《欧盟水框架指令》规定的将水域恢复到良好生态状态的目标，需要控制所有淡水和沿海地区的养分流量。有证据表明，世界范围内流入水体的营养物质正在增加。尽管在欧洲的一些集水区，氮磷浓度最近趋于稳定或有所下降，但据报道，在其他地区，特别是在流经快速发展的经济地区的河流中，氮磷浓度有所增加。溶解有机碳（DOC）流向淡水和波罗的海等沿海地区的通量呈上升趋势，特别是在北温带和寒带地区，向沿海地区的氮和磷出口继续增加。在淡水和沿海水域，对生态系统健康的影响是广泛和不受欢迎的，并且在已知DOC和DON支持供水中致癌物质形成的地方，对人类健康也有影响。如果我们要通过管理干预实现控制目标，详细了解营养物向水体输送的性质、来源和速率是必不可少的，但目前缺乏许多必要的证据基础。常规水体养分监测主要基于无机养分组分，严重低估了从源头到海洋的总养分通量，而研究证实，溶解有机质（DOM）在支持微生物代谢、初级生产和污染物运输等生态系统功能中发挥着重要作用，这表明在常规监测中对其的疏忽可能会破坏国际上控制养分富集影响的努力。在这里，我们以项目成员的具体专业知识为基础，开展了从分子到流域规模的一系列相互关联的实验和观察研究，以解决这一知识差距。我们将结合集水区研究中广泛使用的成熟方法，以及一系列在营养循环研究中应用新颖的前沿方法，或采用新技术，为从分子到河流尺度的营养循环过程控制带来新的见解。该课程将提高对以下方面的理解：1 . DOM在N和P从源头到海洋的运输中的作用，以及在气候变化的情况下，这可能改变向淡水和海岸带的养分输送的方式；在营养状况和DOM特性对比的水体中，DOM作为藻类、植物和微生物群落对养分吸收和利用的来源的生态意义；说谎。来自土壤、牲畜和人类废物的DOM通量对生态状况、淡水提供的商品和服务的影响。它还将提供5个小组和更广泛的科学界之间的知识交流，并在项目的生命周期之外产生影响，通过在当前理解不确定的领域的员工和博士任命来建立能力，破坏商业规划和国际政策制定。

The UN has listed coastal nutrient pollution and hypoxia as the one of the greatest current threats to the global environment. Impacts include eutrophication of coastal waters and oxygen depletion, and the associated damage to ecosystems, biodiversity & coastal water quality. The UNEP Manila Declaration (Jan 2012) identifies nutrient enrichment of the marine environment as one of 3 foci for its Global Programme of Action for the Protection of the Marine Environment from Land-based Activities, and this was one of the key foci at the Rio+20 UN Conference on Sustainable Development, June 2012.Simultaneously, the International Convention on Long-Range Transboundary Air Pollution (CLRTAP) is revising Annex IX of the Gothenburg Protocol (to Abate Acidification, Eutrophication & Ground-level Ozone) to further reduce the emission of ammonia from land-based activities, and in Europe the control of nutrient flux to all freshwaters & the coastal zone is required in order to meet the target of restoring waters to Good Ecological Status under the EU Water Framework Directive.Evidence indicating that nutrient flux to waters is increasing worldwide is clear. Although N & P concentrations have recently levelled off or decreased in some European catchments, in others an increase is reported, particularly in rivers draining through rapidly developing economic regions. A rising trend in Dissolved Organic Carbon (DOC) flux to freshwaters & coastal areas such as the Baltic Sea is also widely reported, particularly across the North Temperate & Boreal regions, where N & P export to the coastal zone continues to rise. Impacts on ecosystem health are extensive & undesirable in both freshwaters & coastal waters, & there are implications for human health where DOC & DON are also known to support carcinogen formation in water supplies.A detailed understanding of the nature, origins & rates of nutrient delivery to waters is essential if we are to meet the target of control through management intervention, yet much of the necessary evidence base is lacking. Routine nutrient monitoring in waters is largely based on inorganic nutrient fractions, and substantially underestimates the total nutrient flux from source to sea, while research confirms that dissolved organic matter (DOM) plays an important role in ecosystem function including supporting microbial metabolism, primary production and pollutant transport, suggesting that its oversight in routine monitoring may undermine international efforts to bring nutrient enrichment impacts under control.Here, we address this knowledge gap, building on the specific expertise of project members, undertaking a suite of interlinked experimental & observational research from molecular to catchment scale. We will use a combination of well-established approaches widely used in catchment research, with a range of cutting-edge approaches which are novel in their application to nutrient cycling research, or employ novel technologies, bringing new insights into the process controls on nutrient cycling at a molecular to river reach scale.The programme will deliver improved understanding of:1. the role of DOM in the transport of N & P from source to sea & the ways in which this might alter nutrient delivery to freshwaters & the coastal zone under a changing climate;2. the ecological significance of DOM as a source of nutrient uptake & utilisation by algal, plant and microbial communities in waters of contrasting nutrient status & DOM character; and3. the impacts of DOM flux from soils, livestock & human waste fluxes on the ecological status, goods & services provided by freshwaters.It will also deliver knowledge exchange between the 5 groups & the wider science community, and have an impact beyond the lifetime of this project, building capacity through staff & PhD appointments in a field where current understanding is uncertain, undermining business planning and international policy development.