Periodic Reporting for period 1 - COSTREAM (Agricultural-climatic interactions on the control of stream dissolved organic matter trends)
Okres sprawozdawczy: 2022-05-01 do 2024-04-30
The rising trends in terrestrial dissolved organic matter (DOM) concentrations in streams have become a serious environmental issue in many catchments of the northern hemisphere. Indeed, DOM impairs water quality and affects the biogeochemical and ecological
functioning of aquatic ecosystems. Knowledge gaps in drivers controlling seasonal and interannual variations of stream DOM limit our ability to provide measures that may be implemented by decision makers in order to mitigate the continuing trends. In rural
landscapes, agricultural practices interact with climatic drivers to affect biogeochemical cycles, however these interactions and their impacts on stream DOM dynamics over different timescales have not been considered so far. The ambition of COSTREAM is to provide
a better understanding of the linkages between management actions and stream DOM variability both spatially and temporally in order to enhance science-based management and restoration solutions. The project combines field and experimental studies in a
well-equipped agricultural catchment with data mining of long-term records collected in the French Brittany region. The main objectives are 1) to investigate the impact of nitrogen mineral fertilizer on the production of terrestrial DOM at the seasonal scale, and
2) to determine how land use management plans during the last decades have interacted with shifts in climatic drivers to regulate stream DOM patterns at the regional scale. The COSTREAM project has potentially strong impacts on both scientific and societal
perspectives.
functioning of aquatic ecosystems. Knowledge gaps in drivers controlling seasonal and interannual variations of stream DOM limit our ability to provide measures that may be implemented by decision makers in order to mitigate the continuing trends. In rural
landscapes, agricultural practices interact with climatic drivers to affect biogeochemical cycles, however these interactions and their impacts on stream DOM dynamics over different timescales have not been considered so far. The ambition of COSTREAM is to provide
a better understanding of the linkages between management actions and stream DOM variability both spatially and temporally in order to enhance science-based management and restoration solutions. The project combines field and experimental studies in a
well-equipped agricultural catchment with data mining of long-term records collected in the French Brittany region. The main objectives are 1) to investigate the impact of nitrogen mineral fertilizer on the production of terrestrial DOM at the seasonal scale, and
2) to determine how land use management plans during the last decades have interacted with shifts in climatic drivers to regulate stream DOM patterns at the regional scale. The COSTREAM project has potentially strong impacts on both scientific and societal
perspectives.
The project was divided in two main WP. The WP1 focused on seasonal dynamics at the soil/stream interface, and was based on field and experimental works. During one hydrological cycle, samples were collected in the riparian area of a well-instrumented catchment and analysed in laboratory conditions. This resulted in a dataset including data on carbon, nitrogen, iron and phosphorus content in soil waters. The second WP focused on long-term dynamics, and was based on public data. An important work of compilation was undertaken, resulting in a large database on long-term (> 20 years) on carbon and nitrogen concentrations in streams and rivers of the Brittany region.
The project has provided a useful contribution to the understanding of environmental regulators of stream dissolved organic carbon (DOC) concentrations in headwater catchments. More specifically, the work carried out at the seasonal and soil columns scales (WP1) evidences the importance of interactions between major biogeochemical cycles (C, N, P and Fe) in regulating the production and consumption mechanisms that drive the amount of mobilisable DOC in riparian soils. This work also highlights very clearly the heterogeneity of catchment processes, pointing to the need to put more effort on DOC dynamics at the soil/stream interface. At the long-term scale (WP2), the results show that stream DOC in Brittany exhibit similar patterns than at the global scale, namely both increasing and decreasing trends despite similar climatic and geomorphological conditions. While decreasing DOC trends seem to be paralleled by an increase in nitrates, the weakness of relationships indicate the need to consider more local geomorphological properties related to the extent of wetlands. Overall, the project has raised important and novel questions about the cumulative effects of soil-water interactions, material transport, and stream conditions.