Sediment oxygen consumption: Role in the global marine carbon cycle

Bo Barker Jørgensen*, Frank Wenzhöfer, Matthias Egger, Ronnie Nøhr Glud

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Abstrakt

The seabed plays a key role in the marine carbon cycle as a) the terminal location of aerobic oxidation of organic matter, b) the greatest anaerobic bioreactor, and c) the greatest repository for reactive organic carbon on Earth. We compiled data on the oxygen uptake of marine sediments with the objective to understand the constraints on mineralization rates of deposited organic matter and their relation to key environmental parameters. The compiled database includes nearly 4000 O2 uptake data and is available as supplementary material. It includes also information on bottom water O2 concentration, O2 penetration depth, geographic position, water depth, and full information on the data sources. We present the different in situ and ex situ approaches to measure the total oxygen uptake (TOU) and the diffusive oxygen uptake (DOU) of sediments and discuss their robustness towards methodological errors and statistical uncertainty. We discuss O2 transport through the benthic and diffusive boundary layers, the diffusion- and fauna-mediated O2 uptake, and the coupling of aerobic respiration to anaerobic processes. Five regional examples are presented to illustrate the diversity of the seabed: Eutrophic seas, oxygen minimum zones, abyssal plains, mid-oceanic gyres, and hadal trenches. A multiple correlation analysis shows that seabed O2 uptake is primarily controlled by ocean depth and sea surface primary productivity. The O2 penetration depth scales with the DOU according to a power law that breaks down under the abyssal ocean gyres. The developed multiple correlation model was used to draw a global map of seabed O2 uptake rates. Respiratory coefficients, differentiated for depth regions of the ocean, were used to convert the global O2 uptake to organic carbon oxidation. The resulting global budget shows an oxidation of 212 Tmol C yr−1 in marine sediments with a 5-95% confidence interval of 175-260 Tmol C yr−1. A comparison with the global flux of particulate organic carbon (POC) from photic surface waters to the deep sea, determined from multiple sediment trap studies, suggests a deficit in the sedimentation flux at 2000 m water depth of about 70% relative to the carbon turnover in the underlying seabed. At the ocean margins, the flux of organic carbon from rivers and from vegetated coastal ecosystems contributes greatly to the budget and may even exceed the phytoplankton production on the inner continental shelf.

OriginalsprogEngelsk
Artikelnummer103987
TidsskriftEarth-Science Reviews
Vol/bind228
Antal sider35
ISSN0012-8252
DOI
StatusUdgivet - maj 2022

Bibliografisk note

Funding Information:
We thank Steven D'Hondt, Jack J. Middelburg, Robert Pockalny, Kenneth L. Smith and Paul Wintersteller for providing data to support our analyses and graphs. We thank Alejandro Ordonez Gloria for helpful discussion on the spatial modeling. We also thank Moritz Holtappels and Steven D'Hondt for helpful comments and references. Reviews by Andy Dale and an anonymous reviewer provided constructive suggestions to improve the manuscript. This work was supported by (a) The Danish National Research Foundation via the Danish Center for Hadal Research (DNRF145), The European commission via an Advanced Grant HADES-ERC (669947), and the Independent Research Fund Denmark (FNU 7014-00078) to RNG, and (b) the Helmholtz Infrastructure Initiative FRAM (?Frontiers of Arctic Marine Monitoring?), the Helmholtz Alliance ROBEX (Robotic Exploration of Extreme Environments), and the Helmholtz Research Program ?Changing Earth ? Sustaining our Future? to FW.

Funding Information:
This work was supported by (a) The Danish National Research Foundation via the Danish Center for Hadal Research ( DNRF145 ), The European commission via an Advanced Grant HADES-ERC ( 669947 ), and the Independent Research Fund Denmark ( FNU 7014-00078 ) to RNG, and (b) the Helmholtz Infrastructure Initiative FRAM (“Frontiers of Arctic Marine Monitoring”), the Helmholtz Alliance ROBEX (Robotic Exploration of Extreme Environments), and the Helmholtz Research Program “Changing Earth – Sustaining our Future” to FW.

Publisher Copyright:
© 2022 The Authors

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