Source to sink: Evolution of lignin composition in the Madre de Dios River system with connection to the Amazon basin and offshore
Abstract
While lignin geochemistry has been extensively investigated in the Amazon River, little is known about lignin distribution and dynamics within deep, stratified river channels or its transformations within soils prior to delivery to rivers. We characterized lignin phenols in soils, river particulate organic matter (POM), and dissolved organic matter (DOM) across a 4 km elevation gradient in the Madre de Dios River system, Peru, as well as in marine sediments to investigate the source-to-sink evolution of lignin. In soils, we found more oxidized lignin in organic horizons relative to mineral horizons. The oxidized lignin signature was maintained during transfer into rivers, and lignin was a relatively constant fraction of bulk organic carbon in soils and riverine POM. Lignin in DOM became increasingly oxidized downstream, indicating active transformation of dissolved lignin during transport, especially in the dry season. In contrast, POM accumulated undegraded lignin downstream during the wet season, suggesting that terrestrial input exceeded in-river degradation. We discovered high concentrations of relatively undegraded lignin in POM at depth in the lower Madre de Dios River in both seasons, revealing a woody undercurrent for its transfer within these deep rivers. Our study of lignin evolution in the soil-river-ocean continuum highlights important seasonal and depth variations of river carbon components and their connection to soil carbon pools, providing new insights into fluvial carbon dynamics associated with the transfer of lignin biomarkers from source to sink.
Additional Information
© 2016 American Geophysical Union. Received 3 JAN 2016; Accepted 4 MAY 2016; Accepted article online 7 MAY 2016; Published online 21 MAY 2016. This work was supported by funding from the U.S. National Science Foundation award 1227192 to A.J.W. and S.J.F., and by funding from the National Program on Key Basic Research Project (2015CB954201) and National Natural Science Foundation of China (41422304) to X.F. R.Z.W. received support from USC funding for undergraduate research. For the river work, we are grateful to field assistance from M. Torres, A. Robles, and A. Ccahuana, and river navigation by Ernesto. Logistical support was provided by Y. Malhi, J. Huaman, W. Huaraca Huasco, and other collaborators as part of the Andes Biodiversity and Ecosystems Research Group (ABERG; andesresearch.org). Thanks to students who assisted in the laboratory work: E. Rosca, K. McPherson, and G. Li (USC), and technical assistance from Nick Rollins. P.M. and A.N. acknowledge funding from Natural Environment Research Council NE/F002149/1 (soils), ARC FT110100457 to P.M. and European Union Marie Curie Fellowship (FP7-2012-329360) to A.N. Funding for the marine samples is acknowledged from NSF (OCE-0934073) to W.B. We are thankful to the captain and crew of the R/V Knorr. We would also like to acknowledge the members of the at-sea and shore-based science party and all contributors to the ANACONDAS project.Attached Files
Published - Feng_et_al-2016-Journal_of_Geophysical_Research__Biogeosciences.pdf
Supplemental Material - jgrg20587-sup-0001-SuppInfo.doc
Supplemental Material - jgrg20587-sup-0002-SuppInfo.pdf
Supplemental Material - jgrg20587-sup-0003-SuppInfo.pdf
Supplemental Material - jgrg20587-sup-0004-SuppInfo.pdf
Supplemental Material - jgrg20587-sup-0005-SuppInfo.pdf
Supplemental Material - jgrg20587-sup-0006-SuppInfo.pdf
Supplemental Material - jgrg20587-sup-0007-SuppInfo.pdf
Supplemental Material - jgrg20587-sup-0008-SuppInfo.xlsx
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Additional details
- Eprint ID
- 79130
- Resolver ID
- CaltechAUTHORS:20170717-112038217
- EAR-1227192
- NSF
- 2015CB954201
- National Programon Key Basic Research Project
- 41422304
- National Natural Science Foundation of China
- University of Southern California
- NE/F002149/1
- Natural Environment Research Council (NERC)
- FT110100457
- Australian Research Council
- FP7-2012-329360
- Marie Curie Fellowship
- OCE-0934073
- NSF
- Created
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2017-07-17Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field