Influence of hydrodynamic processes on the fate of sedimentary organic matter on continental margins

Bao, R., van der Voort, T. S., Zhao, M., Guo, X., Montluçon, D. B., McIntyre, C. and Eglinton, T. I. (2018) Influence of hydrodynamic processes on the fate of sedimentary organic matter on continental margins. Global Biogeochemical Cycles, 32(9), pp. 1420-1432. (doi: 10.1029/2018GB005921)

Abstract

Understanding the effects of hydrodynamic forcing on organic matter (OM) composition is important for assessment of organic carbon (OC) burial in marginal seas on regional and global scales. Here we examine the relationships between regional oceanographic conditions (bottom shear stress), and the physical characteristics (mineral surface area and grain size) and geochemical properties (OC content [OC%] and carbon isotope compositions [13C, 14C]) of a large suite of surface sediments from the Chinese marginal seas to assess the influence of hydrodynamic processes on the fate of OM on shallow continental shelves. Our results suggest that 14C content is primarily controlled by organo‐mineral interactions and hydrodynamically driven resuspension processes, highlighted by (i) positive correlations between 14C content and OC% (and surface area) and (ii) negative correlations between 14C content and grain size (and bottom shear stress). Hydrodynamic processes influence 14C content due to both OC aging during lateral transport and accompanying selective degradation of OM associated with sediment (re) mobilization, these effects being superimposed on the original 14C characteristics of carbon source. Our observations support the hypotheses of Blair and Aller (2012, https://doi.org/10.1146/annurev‐marine‐120709‐142717) and Leithold et al. (2016, https://doi.org/10.1016/j.earscirev.2015.10.011) that hydrodynamically driven sediment translocation results in greater OC 14C depletion in broad, shallow marginal seas common to passive margin settings than on active margins. On a global scale, this may influence the extent to which continental margins act as net carbon sources and sinks. Our findings thus suggest that hydrodynamic processes are important in shaping the nature, dynamics, and magnitude of OC export and burial in passive marginal seas.

• Item Type: Articles
• Additional Information: This study was supported by SNF “CAPS-LOCK” project 200021_140850 (T. I. E.) ,by the National Natural Science Foundation of China (grants 41520104009 and 41521064, M. Z.) and by the “111” project (B13030).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Mcintyre, Dr Cameron
• Authors: Bao, R., van der Voort, T. S., Zhao, M., Guo, X., Montluçon, D. B., McIntyre, C., and Eglinton, T. I.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Global Biogeochemical Cycles
• Publisher: American Geophysical Union
• ISSN: 0886-6236
• ISSN (Online): 1944-9224
• Published Online: 20 September 2018
• Copyright Holders: Copyright © 2018 The Authors
• First Published: First published in Global Biogeochemical Cycles 32(9): 1420-1432
• Publisher Policy: Reproduced under a Creative Commons License