COSTREAM · Agricultural-climatic interactions on the control of stream dissolved organic matter trends

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 will combine 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. Thanks to this project, the experienced researcher will receive a unique multidisciplinary scientific training by INRAE that will reinforce significantly his expertise for future research activities and open new perspectives for both academic and non-academic careers.