In order to meet the project objectives, a suite of interlinked experimental and observational research from molecular to catchment scale is being undertaken. A complimentary mixture of approaches are used including well established quantitative catchment science observation and measurement, novel sensor technologies for high frequency observation of DOM and related parameters in river systems, with a range of cutting-edge approaches which are either novel in their application to biogeochemical cycling research, or employ novel technologies which bring new insights into the process controls on nutrient cycling at molecular to river reach scale. The DOMAINE research programme is structured through a suite of linked work packages (WP1-4) with research ranging from field monitoring and laboratory analysis of field samples, to experimental research under controlled conditions. The aims and approaches of each work package are summarised below:
Work Package 1
WP1 have setup and are maintaining a set of high resolution instream monitoring stations and equipment (click here for more information) WP1 are collecting data from a wide range of source areas to asses spatial variability in DOM chemistry across the monitoring catchments. The main aims of WP1 are to determine (1) The origins and rates of DOC, DON and DOP flux to aquatic ecosystems from catchment sources, relative to total C, N and P flux as they vary in time and space in relation to atmospheric inputs, catchment character, hydrological function and the extent of nutrient enrichment (2) The magnitude and character of the DOC, DON and DOP pools instream as they vary in relation to source character, season, hydromorphology, inorganic nutrient flux behaviours, microbial activity and biological production. Additional work is being undertaken examining fluorescence and UV absorption in order to further characterise the DOM pool.
Work Package 2
WP2 is focusing on molecular level identification and quantification of the DOM pool. The analysis is using a combination of analytical techniques, including high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. A metabolomics approach is also being taken to identify compounds of interest in water and soil samples from the catchments. Bulk characterisation techniques including amino acid and carbohydrate analysis, and fluorescence emission spectroscopy is being used in conjunction to complement the high resolution techniques. In addition to the analysis of grab samples, work is aimed at developing the use of in situ passive sampling techniques (POCIS) tailored to the determination of DOC, DON and DOP in freshwaters.
Work Package 3
This work package is focusing on the flux and inter-relationships of the DOC, DON and DOP pools. Specifically, this work package aims to, (1) employ high performance metabolome profiling to obtain a broad-scale assessment of the dominant enzymatic pathways operating in freshwater environments in specific relation to both the high and low MW components, (2) use of isotopic tracer techniques to evaluate the flux of low MW solutes through different components of the freshwater ecosystem, and (3) use conventional bioavailability assays to assess the metabolism of high MW solutes. This combination of techniques allows us to identify (1) the critical bottlenecks in organic C, N and P cycling, (2) the potential interactions of the C, N and P cycles, (3) the contribution of specific compounds to biological productivity in different habitats, and to (4) make inferences regarding compound source-apportionment based on pool size and flux rate calculations, and (5) quantify the potential distance that specific solutes may be transported down a catchment.
Work Package 4
This work complements the information gained in all work packages focusing on the bioavailability of DON and DOP to riverine phytoplankton epilithic algae and macrophytes. We are testing the hypothesis that the ability to utilize DON and DOP, especially the high molecular weight forms, will depend on community composition and the extent of nutrient limitation. In addition, availability of organic P compounds will be assayed using different types of DOP such as ATP, DNA, and phosphonoacetates. Furthermore epilithic algal samples and the widespread submerged bryophyte Fontinalis antipyretica are undergoing stable-isotope analyses of their δ13C and δ15N organic content.