DECOUPLING OF DISSOLVED ORGANIC MATTER PATTERNS BETWEEN STREAM AND RIPARIAN GROUNDWATER IN A HEADWATER FORESTED CATCHMENT
Streams are important sources of carbon to the atmosphere, though whether they merely outgas allochthonous carbon dioxide or mineralize allochthonous dissolved organic matter (DOM) is still under debate. For a year, we analyzed DOM concentration and its chromophoric properties along a forested headwater stream (3.7 km reach) and adjacent riparian groundwater (GW). For both stream water and riparian GW, DOM had an eminently protein-like character and was originated mostly from microbial sources and recent biological activity. However, dissolved organic carbon (DOC) and nitrogen (DON) concentrations as well as spectroscopic indexes differed between the two water compartments. During the leaf litter period, stream DOM concentrations were higher and its spectroscopic signature had a major influence of terrestrial vegetation than riparian GW. In-stream processes along the reach contributed to reduce DOC and DON fluxes by 50% and 30%, respectively. Yet, DOC and DON uptake were unrelated to each other, suggesting different biogeochemical pathways. Our study highlights that stream DOM is not merely a reflection of riparian GW entering the stream and that headwater streams have the capacity to internally produce, transform, and consume DOM.
Eugènia Martí (Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), firstname.lastname@example.org;
Susana Bernal (Primary Presenter/Author), Center for Advanced Studies of Blanes (CEAB-CSIC), email@example.com;
Anna Lupon (Co-Presenter/Co-Author), Swedish University of Agricultural Sciences, firstname.lastname@example.org;
Núria Catalan (Co-Presenter/Co-Author), Catalan Institute for Water Research (ICRA), email@example.com;
Sara Castelar (Co-Presenter/Co-Author), Center for Advanced Studies of Blanes (CEAB-CSIC), firstname.lastname@example.org;