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

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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.