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Vegetal Undercurrents—Obscured Riverine Dynamics of Plant Debris

Schwab, Melissa S.; Hilton, Robert G.; Haghipour, Negar; Baronas, J. Jotautas; Eglinton, Timothy I.


Melissa S. Schwab

Robert G. Hilton

Negar Haghipour

Timothy I. Eglinton


Much attention has been focused on fine-grained sediments carried as suspended load in rivers due to their potential to transport, disperse, and preserve organic carbon (OC), while the transfer and fate of OC associated with coarser-grained sediments in fluvial systems have been less extensively studied. Here, sedimentological, geochemical, and biomolecular characteristics of sediments from river depth profiles reveal distinct hydrodynamic behavior for different pools of OC within the Mackenzie River system. Higher radiocarbon (14C) contents, low N/OC ratios, and elevated plant-derived biomarker loadings suggest a systematic transport of submerged vascular plant debris above the active riverbed in large channels both upstream of and within the delta. Subzero temperatures hinder OC degradation promoting the accumulation and waterlogging of plant detritus within the watershed. Once entrained into a channel, sustained flow strength and buoyancy prevent plant debris from settling and keep it suspended in the water column above the riverbed. Helical flow motions within meandering river segments concentrate lithogenic and organic debris near the inner river bends forming a sediment-laden plume. Moving offshore, we observe a lack of discrete, particulate OC in continental shelf sediments, suggesting preferential trapping of coarse debris within deltaic and neritic environments. The delivery of waterlogged plant detritus transport and high sediment loads during the spring flood may reduce oxygen exposure times and microbial decomposition, leading to enhanced sequestration of biospheric OC. Undercurrents enriched in coarse, relatively fresh plant fragments appear to be reoccurring features, highlighting a poorly understood yet significant mechanism operating within the terrestrial carbon cycle.


Schwab, M. S., Hilton, R. G., Haghipour, N., Baronas, J. J., & Eglinton, T. I. (2022). Vegetal Undercurrents—Obscured Riverine Dynamics of Plant Debris. Journal of Geophysical Research: Biogeosciences, 127(3), Article e2021JG006726.

Journal Article Type Article
Acceptance Date Mar 2, 2022
Online Publication Date Mar 9, 2022
Publication Date 2022-03
Deposit Date Dec 19, 2023
Journal Journal of Geophysical Research: Biogeosciences
Print ISSN 2169-8953
Electronic ISSN 2169-8961
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 127
Issue 3
Article Number e2021JG006726
Keywords Paleontology; Atmospheric Science; Soil Science; Water Science and Technology; Ecology; Aquatic Science; Forestry
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