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Drought-induced discontinuities in the source and degradation of dissolved organic matter in a Mediterranean river
Catalan Inst Water Res ICRA, Emili Grahit 101, Girona 17003, Spain..
UFZ Helmholtz Ctr Environm Res, Dept Lake Res, Bruckstr 3a, D-39114 Magdeburg, Germany..
Univ Basque Country, Fac Sci & Technol, Dept Plant Biol & Ecol, Apdo 644, Bilbao 48080, Spain..
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
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2016 (English)In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 127, no 1, 125-139 p.Article in journal (Refereed) PublishedText
Abstract [en]

The composition of dissolved organic matter (DOM) in rivers results from the different sources and in-stream transformations along the land to ocean aquatic continuum. Riverine DOM sources are highly dependent on the hydrological connection between the river channel and the surrounding terrestrial ecosystems, but how the lack of this connectivity (e.g., during drought episodes) affects the sources and biodegradation of DOM in rivers remains unclear. Here we identified the DOM sources as well as the different DOM pools that are respired along a Mediterranean river during drought by combining absorbance-fluorescence spectroscopy, size-exclusion chromatography, biodegradation assays, and stable and radiocarbon isotopes. DOM composition was highly heterogeneous along the river in response to different sources and in-stream processes in each distinct aquatic environment (i.e., isolated water pools, running waters, and impounded waters in weirs). The reduced hydrological connectivity with terrestrial ecosystems promoted the influence of autochthonous DOM sources. Still, tree leaves from overhanging canopies stood out as an important terrestrial DOM source, especially in sites where water residence time was high such as isolated pools and weirs. Degradation of leaf leachates was a relevant process in these sites, whereas autochthonous DOM and groundwater millennial DOM (> 1300 year B.P.) seemed to be degraded in running waters. Overall, our results highlight that the drought-induced hydrological disconnection entails a great spatial heterogeneity in the sources of DOM, which at the same time determines the different DOM pools that are respired in each environment along the river.

Place, publisher, year, edition, pages
2016. Vol. 127, no 1, 125-139 p.
Keyword [en]
Mediterranean rivers, Drought, Dissolved organic matter, Degradation, Radiocarbon
National Category
Ecology Oceanography, Hydrology, Water Resources
URN: urn:nbn:se:uu:diva-280090DOI: 10.1007/s10533-015-0173-5ISI: 000368722700009OAI: oai:DiVA.org:uu-280090DiVA: diva2:910137
Wenner-Gren Foundations
Available from: 2016-03-08 Created: 2016-03-08 Last updated: 2016-03-08Bibliographically approved

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