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

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Vonk, Jorien E., Drenzek, Nicholas J., Hughen, Konrad A., Stanley, Rachel H. R., McIntyre, Cameron P., Montlucon, Daniel B., Giosan, Liviu, Southon, John R., Santos, Guaciara M., Druffel, Ellen R. M., Andersson, August A., Sköld, Martin, Eglinton, Timothy I.
• Format: Report
• Language: English
• Published: 2018
• Subjects: Terrestrial carbon; Organic matter; Radiocarbon; Leaf waxes; Sediment; Residence time; Mackenzie Delta; permafrost
• Online Access: https://hdl.handle.net/1912/10799

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 244 (2019): 502-521, doi:10.1016/j.gca.2018.09.034. 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 predepositional histories. Here, we examine down-core 14C profiles of higher plant leaf waxderived fatty acids isolated from high fidelity sedimentary sequences spanning the socalled “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 ...