River channel connectivity shifts metabolite composition and dissolved organic matter chemistry

• Published in: Nature communications Vol. 10; no. 1; p. 459
• Main Authors: Lynch, Laurel M., Sutfin, Nicholas A., Fegel, Timothy S., Boot, Claudia M., Covino, Timothy P., Wallenstein, Matthew D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 28.01.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 140/58; 704/172/169; 704/242; 704/47/4112; 704/47/4113; Aquatic ecosystems; Carbon - analysis; Carbon sequestration; Colorado; Composition; Dissolved organic matter; Downstream; Ecosystem; Ecosystem management; Energy storage; Floodplains; Fluorescence; Fluorescence spectroscopy; Food chains; Food quality; Food webs; Geography; Geomorphology; Heterogeneity; Humanities and Social Sciences; Hydrology; Mass Spectrometry; Mass spectroscopy; Metabolism; Microorganisms; multidisciplinary; Organic Chemicals - analysis; Organic chemistry; Rivers; Rivers - chemistry; Science; Science (multidisciplinary); Seasons; Segments; Spectrometry, Fluorescence; Water - analysis; Water Pollutants - analysis; Water Quality; Watershed management; Colorado
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-08406-8

Biogeochemical processing of dissolved organic matter (DOM) in headwater rivers regulates aquatic food web dynamics, water quality, and carbon storage. Although headwater rivers are critical sources of energy to downstream ecosystems, underlying mechanisms structuring DOM composition and reactivity are not well quantified. By pairing mass spectrometry and fluorescence spectroscopy, here we show that hydrology and river geomorphology interactively shape molecular patterns in DOM composition. River segments with a single channel flowing across the valley bottom export DOM with a similar chemical profile through time. In contrast, segments with multiple channels of flow store large volumes of water during peak flows, which they release downstream throughout the summer. As flows subside, losses of lateral floodplain connectivity significantly increase the heterogeneity of DOM exported downstream. By linking geomorphologic landscape-scale processes with microbial metabolism, we show DOM heterogeneity increases as a function of fluvial complexity, with implications for ecosystem function and watershed management. The underlying mechanisms structuring dissolved organic matter (DOM) composition and reactivity in rivers remain poorly quantified. Here, the authors pair mass spectrometry and fluorescence spectroscopy to show that hydrology and river geomorphology both shape molecular patterns in DOM composition.