Elsevier

Organic Geochemistry

Volume 115, January 2018, Pages 138-155
Organic Geochemistry

Invited Review
Centers of organic carbon burial and oxidation at the land-ocean interface

https://doi.org/10.1016/j.orggeochem.2017.09.008Get rights and content

Abstract

Continental margin systems collectively receive and store vast amounts of organic carbon (OC) derived from primary productivity both on land and in the ocean, thereby playing a central role in the global carbon cycle. The land-ocean interface is however extremely heterogeneous in terms of terrigenous input, marine primary productivity, sediment transport processes and depositional conditions (e.g. such as bottom water oxygen level). Continental margins are also highly dynamic, with processes occurring over a broad range of spatial and temporal scales. The rates of OC burial and oxidation are consequently variable over both space and time, hindering our ability to derive a global picture of OC cycling at the land-ocean interface. Here, we review the processes controlling the fate of organic matter in continental margin sediments, with a special emphasis on “hot spots” and “hot moments” of OC burial and oxidation. We present a compilation of compositional data from a set of illustrative settings, including fjords, small mountainous river margins, large deltaic systems and upwelling areas. Bulk OC stable isotope and radiocarbon compositions reveal the diversity and complexity characteristic of OC buried in marginal seas. This primarily relates to differences in marine and terrestrial inputs, the composition of the terrestrial component (e.g. vascular plant OC, soil, and petrogenic OC inputs), and processes modulating the fate of OC within the marine environment (e.g. priming). This widely contrasting behavior of OC among these systems illustrates that the reactivity of OC is a product of its chemical composition and regional conditions. Interpreted in the context of bulk compositional data as well as that obtained on specific molecular markers (e.g. lignin-derived phenols), the possibility exists to tease apart complex mixtures of terrestrial and marine inputs, and to shed light on the role of the myriad of depositional and post-depositional processes. Finally, we discuss a set of hot topics that warrant further investigation – such as the role of photochemistry, fungi, halogenation and reactive iron in dictating the fate of OC in the (changing) coastal ocean.

Introduction

Mitigating and adapting to global environmental change associated with land-use and climate are among society’s grand challenges for the future. A corresponding challenge in carbon (C)-cycle research is the determination of global inventories and fluxes in a heterogeneous, dynamic world. Rates and inventories are uneven spatially and temporally. Scientists often gravitate to regions where inventories, rates and/or fluxes are the highest because they provide a greater than average accounting per unit area relative to sampling effort. Here, we adopt the convention of McClain et al. (2003), who defined biogeochemical hot spots as “patches that show disproportionately high reaction rates relative to the surrounding matrix” and hot moments as “short periods of time that exhibit disproportionately high reaction rates relative to longer intervening time periods.” The hot spots and/or moments provide useful insights in to processes, all the more necessary if we are to understand how the Earth System will respond to future anthropogenic perturbations. In this review, hot spots and moments within the continental margin, a zone that has been characterized itself as a global hot spot in terms of C-sequestration over geological timescales, will be discussed from the perspective of the controls on C-burial and/or oxidation, as well as the character of the organic C reaching sedimentary systems.

Section snippets

Background: a primer on OC burial in the coastal ocean margin

The major hot spot for the burial of much of the organic carbon (OC) in the global ocean is the coastal margin. In particular, river delta and non-deltaic shelf regions bury an estimated 114 Tg C/year and 70 Tg C/year, respectively, with only ca. 6 Tg C/year buried in the open ocean (Burdige, 2005). While there has been longstanding general agreement that continental shelves represent the largest sink of both terrestrial (OCterr) and marine (OCmar) OC in the global ocean (Berner, 1982, Hedges,

Our approach

The behavior of OC in terms of whether it is oxidized or ultimately preserved via burial in the seabed has often been described to be a result of the “labile” or “refractory” nature of the OC (Bianchi, 2011, Schmidt et al., 2011). These terms, which are commonly used to describe differences in the quality of OC as a food resource for heterotrophs, may only be valid in the context of the ambient environment and over a particular timescale of observations (Burdige, 2006). In reality, the

Linkages between depositional environments, OC and mineral-aggregate associations and hydrodynamic sorting

The OC entering coastal hotspots is typically characterized as a variable mixture of vascular plant, algal debris, diagenetically-altered material (e.g. aged soil C and resuspended sedimentary OC), and petrogenic OC (primarily on active margins) derived from the weathering of sedimentary rocks (Blair and Aller, 2012). These components reside across a range of particle density and size and thereby are susceptible to partial separation via hydrodynamic sorting prior to final burial (Wakeham et

Linkages between residence time and bulk OC age, abundance and source

The average composition of the OC that is transported to the coastal ocean strongly reflects properties of the watershed and the residence time of OC and sediments therein (Blair and Aller, 2012). In general, residence times in small, mountainous drainage basins characteristic of active margins and rapidly eroding source regions are less than the residence times in low-gradient river systems with extensive lowlands, the latter often characteristic of passive tectonic margins. This results in

Lignin biomarkers as tools for assessing the fate of terrestrial OC

Lignin may be the most extensively studied terrestrial biomarker because of its abundance. It is the second most abundant biopolymer on Earth, constituting ca. 20–30% of vascular plant tissue (Kirk and Farrell, 1987), and mechanisms of its breakdown and preservation are thus an important aspect of Earth’s carbon cycle. In fact, the high rate of carbon burial in coastal systems has been in large part attributed to delivery of terrestrial plant-and soil-sourced OC that has been stabilized by its

Future questions and directions

How do biomarkers and isotopes reflect differences in the spatio-temporal evolution of organic matter signals – from pre-aging, deposition, redistribution and burial in “hotspot” environments and during “hot moment” events? What additional information can be gained from biomarkers, which in many cases only represent a relatively small fraction of the TOC, beyond that obtained from bulk measurements? How can serial oxidation methods (e.g. ramped PyrOx) be used to bridge the gap between bulk and

Overview

  • 1.

    Coastal systems represent potential hot spots and hot moments of carbon burial and oxidation at the land-ocean interface. To better understand how the Anthropocene is altering the mineralization and burial of OC in different zones of the coastal ocean, more emphasis needs to be made on the spatial heterogeneity, as demonstrated in Critical Zone Observatory (CZO) work (largely in terrestrial systems).

  • 2.

    The relationship between %OC, average grain size and surface area in surface sediments continues

Acknowledgements

We would to thank the reviewers for their helpful comments, which greatly improved this manuscript. T.S.B. would also like to thank the Jon and Beverly Thompson Chair for providing funds that were in part, used to support work on this manuscript. Finally, we would like to thank Dr. Rui Bao for his help with modifications to Fig. 4.

References (255)

  • T.S. Bianchi et al.

    Temporal variability in terrestrially-derived sources of particulate organic carbon in the lower Mississippi River and its upper tributaries

    Geochimica et Cosmochimica Acta

    (2007)
  • N.E. Blair et al.

    From bedrock to burial: the evolution of particulate organic carbon across coupled watershed-continental margin systems

    Marine Chemistry

    (2004)
  • N.E. Blair et al.

    The persistence of memory: the fate of ancient sedimentary organic carbon in a modern sedimentary system

    Geochimica et Cosmochimica Acta

    (2003)
  • J. Bouchez et al.

    Source, transport and fluxes of Amazon River particulate organic carbon: insights from river sediment depth-profiles

    Geochimica et Cosmochimica Acta

    (2014)
  • A.B. Burd et al.

    Assessing the apparent imbalance between geochemical and biochemical indicators of meso-and bathypelagic biological activity: what the@ $♯! is wrong with present calculations of carbon budgets?

    Deep Sea Research Part II: Topical Studies in Oceanography

    (2010)
  • D.E. Canfield

    Factors influencing organic carbon preservation in marine sediments

    Chemical Geology

    (1994)
  • L. Coppola et al.

    The importance of ultrafine particles as a control on the distribution of organic carbon in Washington Margin and Cascadia Basin sediments

    Chemical Geology

    (2007)
  • D.R. Corbett et al.

    An evaluation of mobile mud dynamics in the Mississippi River deltaic region

    Marine Geology

    (2004)
  • X. Cui et al.

    Biospheric and petrogenic organic carbon flux along southeast Alaska

    Earth and Planetary Science Letters

    (2016)
  • X. Cui et al.

    Organic carbon burial in fjords: terrestrial versus marine inputs

    Earth and Planetary Science Letters

    (2016)
  • K.J. Curry et al.

    Direct visualization of clay microfabric signatures driving organic matter preservation in fine-grained sediment

    Geochimica et Cosmochimica Acta

    (2007)
  • D. DeMaster et al.

    Deposition of bomb 14C in continental slope sediments of the Mid-Atlantic Bight: assessing organic matter sources and burial rates

    Deep Sea Research Part II: Topical Studies in Oceanography

    (2002)
  • A.F. Dickens et al.

    Solid-state 13C NMR analysis of size and density fractions of marine sediments: insight into organic carbon sources and preservation mechanisms

    Geochimica et Cosmochimica Acta

    (2006)
  • A.F. Diefendorf et al.

    Distribution and carbon isotope patterns of diterpenoids and triterpenoids in modern temperate C3 trees and their geochemical significance

    Geochimica et Cosmochimica Acta

    (2012)
  • N.J. Drenzek et al.

    Constraints on the origin of sedimentary organic carbon in the Beaufort Sea from coupled molecular 13C and 14C measurements

    Marine Chemistry

    (2007)
  • C.S. Foote

    Photosensitized oxidation and singlet oxygen: consequences in biological systems

    Free Radicals in Biology

    (1976)
  • M.-A. Galeron et al.

    Oxidation products of betulin: new tracers of abiotic degradation of higher plant material in the environment

    Organic Geochemistry

    (2016)
  • V. Galy et al.

    The provenance of vegetation and environmental signatures encoded in vascular plant biomarkers carried by the Ganges-Brahmaputra rivers

    Earth and Planetary Science Letters

    (2011)
  • L. Giosan et al.

    Recent morphodynamics of the Indus delta shore and shelf

    Continental Shelf Research

    (2006)
  • M.A. Goni et al.

    Distribution and sources of particulate organic matter in the water column and sediments of the Fly River Delta, Gulf of Papua (Papua New Guinea)

    Estuarine, Coastal and Shelf Science

    (2006)
  • M.A. Goñi et al.

    Fungal degradation of wood lignins: geochemical perspectives from CuO-derived phenolic dimers and monomers

    Geochimica et Cosmochimica Acta

    (1993)
  • M.A. Goñi et al.

    A reassessment of the sources and importance of land-derived organic matter in surface sediments from the Gulf of Mexico

    Geochimica et Cosmochimica Acta

    (1998)
  • M.A. Goñi et al.

    The supply and preservation of ancient and modern components of organic carbon in the Canadian Beaufort Shelf of the Arctic Ocean

    Marine Chemistry

    (2005)
  • M.A. Goñi et al.

    Distribution and sources of organic biomarkers in arctic sediments from the Mackenzie River and Beaufort Shelf

    Marine Chemistry

    (2000)
  • E.S. Gordon et al.

    Sources and distribution of terrigenous organic matter delivered by the Atchafalaya River to sediments in the northern Gulf of Mexico

    Geochimica et Cosmochimica Acta

    (2003)
  • E.S. Gordon et al.

    Controls on the distribution and accumulation of terrigenous organic matter in sediments from the Mississippi and Atchafalaya river margin

    Marine Chemistry

    (2004)
  • E.S. Gordon et al.

    Organic matter distribution and accumulation on the inner Louisiana shelf west of the Atchafalaya River

    Continental Shelf Research

    (2001)
  • G.W. Gribble

    The diversity of naturally produced organohalogens

    Chemosphere

    (2003)
  • G. Griffiths et al.

    Input of river-derived sediment to the New Zealand continental shelf: I. Mass

    Estuarine, Coastal and Shelf Science

    (1985)
  • D.R. Griffith et al.

    The radiocarbon age of organic carbon in marine surface sediments

    Geochimica et Cosmochimica Acta

    (2010)
  • A.C.I.A. ACIA

    Forests, land management and agriculture

    Arctic Climate Impact Assessment

    (2005)
  • R.C. Aller et al.

    Early diagenetic cycling, incineration, and burial of sedimentary organic carbon in the central Gulf of Papua (Papua New Guinea)

    Journal of Geophysical Research: Earth Surface

    (2008)
  • M.A. Allison et al.

    Carbon burial on river-dominated continental shelves: impact of historical changes in sediment loading adjacent to the Mississippi River

    Geophysical Research Letters

    (2007)
  • A.H. Altieri et al.

    Climate change and dead zones

    Global Change Biology

    (2015)
  • P. Baldrian et al.

    Degradation of cellulose by basidiomycetous fungi

    FEMS Microbiology Reviews

    (2008)
  • F. Baltar et al.

    High dissolved extracellular enzymatic activity in the deep central Atlantic Ocean

    Aquatic Microbial Ecology

    (2010)
  • R. Bao et al.

    Widespread dispersal and aging of organic carbon in shallow marginal seas

    Geology

    (2016)
  • A. Barber et al.

    Preservation of organic matter in marine sediments by inner-sphere interactions with reactive iron

    Science Reports

    (2017)
  • J.E. Bauer et al.

    The changing carbon cycle of the coastal ocean

    Nature

    (2013)
  • R. Benner et al.

    Biogeochemical cycling of lignocellulosic carbon in marine and freshwater ecosystems: relative contributions of procaryotes and eucaryotes

    Limnology and Oceanography

    (1986)
  • Cited by (0)

    View full text