Temporal deconvolution of vascular plant-derived fatty acids exported from terrestrial watersheds

Jorien E. Vonk*, Nicholas J. Drenzek, Konrad A. Hughen, Rachel H.R. Stanley, Cameron McIntyre, Daniel B. Montluçon, Liviu Giosan, John R. Southon, Guaciara M. Santos, Ellen R.M. Druffel, August A. Andersson, Martin Sköld, Timothy I. Eglinton

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review

23 Downloads (Pure)

Abstract

Relatively little is known about the amount of time that lapses between the photosynthetic fixation of carbon by vascular land plants and its incorporation into the marine sedimentary record, yet the dynamics of terrestrial carbon sequestration have important implications for the carbon cycle. Vascular plant carbon may encounter multiple potential intermediate storage pools and transport trajectories, and the age of vascular plant carbon accumulating in marine sediments will reflect these different pre-depositional histories. Here, we examine down-core 14C profiles of higher plant leaf wax-derived fatty acids isolated from high fidelity sedimentary sequences spanning the so-called “bomb-spike” and encompassing a ca. 60-degree latitudinal gradient from tropical (Cariaco Basin), temperate (Saanich Inlet), and polar (Mackenzie Delta) watersheds to constrain integrated vascular plant carbon storage/transport times (“residence times”). Using a modeling framework, we find that, in addition to a “young” (conditionally defined as < 50 y) carbon pool, an old pool of compounds comprises 49 to 78 % of the fractional contribution of organic carbon (OC) and exhibits variable ages reflective of the environmental setting. For the Mackenzie Delta sediments, we find a mean age of the old pool of 28 ky (±9.4, standard deviation), indicating extensive pre-aging in permafrost soils, whereas the old pools in Saanich Inlet and Cariaco Basin sediments are younger, 7.9 (±5.0) and 2.4 (±0.50) to 3.2 (±0.54) ky, respectively, indicating less protracted storage in terrestrial reservoirs. The “young” pool showed clear annual contributions for Saanich Inlet and Mackenzie Delta sediments (comprising 24% and 16% of this pool, respectively), likely reflecting episodic transport of OC from steep hillside slopes surrounding Saanich Inlet and annual spring flood deposition in the Mackenzie Delta, respectively. Contributions of 5–10 year old OC to the Cariaco Basin show a short delay of OC inflow, potentially related to transport time to the offshore basin. Modeling results also indicate that the Mackenzie Delta has an influx of young but decadal material (20–30 years of age), pointing to the presence of an intermediate reservoir. Overall, these results show that a significant fraction of vascular plant C undergoes pre-aging in terrestrial reservoirs prior to accumulation in deltaic and marine sediments. The age distribution, reflecting both storage and transport times, likely depends on landscape-specific factors such as local topography, hydrographic characteristics, and mean annual temperature of the catchment, all of which affect the degree of soil buildup and preservation. We show that catchment-specific carbon residence times across landscapes can vary by an order of magnitude, with important implications both for carbon cycle studies and for the interpretation of molecular terrestrial paleoclimate records preserved in sedimentary sequences.

Original languageEnglish
Pages (from-to)502-521
Number of pages20
JournalGeochimica et Cosmochimica Acta
Volume244
Early online date9 Oct 2018
DOIs
Publication statusPublished - 1 Jan 2019

Funding

We thank Sheila Griffin for assistance with AMS target preparation, Carl Johnson for compound-specific δ 13 C and elemental analysis expertise, Ana Lima for freeze core sampling guidance, NOSAMS for 14 C analysis and use of their PCGC facility, and the crews of the R/V Clifford Barnes and R/V Hermano Gines for their help in retrieving sediment cores from the Saanich Inlet and Cariaco Basin, respectively. For Mackenzie sediment core sampling we wish to thank William Hurst, Tommy Smith, Dennis Felix and the Aurora Research Institute , the Inuvialuit Land Administration and the Gwich'in Renewable Resource Board, as well as Valier Galy, Sarah Brody, David Griffith, Marshall Moore, Skye Moret, Michaelene Nelson, Camilo Ponton, and Rebecca Sorrell. We would like to thank two anonymous reviewers and Robert Hilton for providing insightful comments. Financial support was provided by a Schlanger Ocean Drilling Graduate Fellowship (NJD) , an EPA STAR Graduate Fellowship (NJD) , a Dutch NWO Veni grant #825.10.022 (JEV), US NSF grants #OCE-0137005 (TIE and KAH), #OCE-052626800 (TIE), #OCE-0961980 (ERMD), and #EAR-0447323 (ERMD and JRS), a Swiss SNF grant #200021_140850 (TIE), a Swedish Research Council grant #2013-05204 (MS), as well as the Stanley Watson Chair for Excellence in Oceanography at WHOI (TIE) and the WHOI Arctic Research Initiative (TIE and LG). Appendix A

FundersFunder number
National Science Foundation1755125, -0447323, -0961980, -0137005, -052626800
Woods Hole Oceanographic Institution
Aurora Research Institute
Environmental Protection Agency
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung200021_140850
Nederlandse Organisatie voor Wetenschappelijk Onderzoek825.10.022
Vetenskapsrådet2013-05204

    Keywords

    • Leaf waxes
    • Organic matter
    • Radiocarbon
    • Residence time
    • Sediment
    • Terrestrial carbon

    Fingerprint

    Dive into the research topics of 'Temporal deconvolution of vascular plant-derived fatty acids exported from terrestrial watersheds'. Together they form a unique fingerprint.

    Cite this