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Rapid Organic Matter Sulfurization in Sinking Particles from the Cariaco Basin Water Column

Raven, Morgan Reed and Sessions, Alex L. and Adkins, Jess F. and Thunell, Robert C. (2016) Rapid Organic Matter Sulfurization in Sinking Particles from the Cariaco Basin Water Column. Geochimica et Cosmochimica Acta, 190 . pp. 175-190. ISSN 0016-7037.

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Organic matter (OM) burial in marine sediments is a potentially important control on global climate and the long-term redox state of the earth’s surface. Still, we have only a limited understanding of the processes that stabilize OM and facilitate its preservation in the geologic record. Abiotic reactions with (poly)sulfides can enhance the preservation potential of OM, but for this process to be significant it needs to compete with OM remineralization, the majority of which occurs before sinking particles reach the sea floor. Here we investigate whether OM sulfurization occurs within sinking particles in the Cariaco Basin, a modern sulfidic marine environment with high rates of OM burial. Proto-kerogen in sinking particles is frequently more sulfur-rich and ^(34)S-depleted than expectations for biomass, with a composition that is difficult to explain by mixing with resuspended or terrigenous material. Instead, it appears that sulfur is being incorporated into OM on a timescale of days in sinking particles. The flux of this abiogenic organic S from particles is equivalent to approximately two-thirds of the total amount of proto-kerogen S at 10 cm depth in underlying sediments (ODP Core 1002B); after 6000 years of more gradual sulfurization reactions, potential water column sources are still equivalent to nearly half of the total proto-kerogen S in Cariaco sediments. Water column sulfurization is most extensive during periods of upwelling and high primary productivity and appears to involve elemental S, possibly via polysulfides. This process has the potential to deliver large amounts of OM to the sediments by making it less available for remineralization, generating OM-rich deposits. It represents a potentially dynamic sink in the global carbon cycle that can respond to changes in environmental conditions, including the size and intensity of O_2-depleted environments. Water column OM sulfurization could also have played a more significant role in the carbon cycle during ocean anoxic events, for example during the Cretaceous.

Item Type:Article
Related URLs:
URLURL TypeDescription
Sessions, Alex L.0000-0001-6120-2763
Adkins, Jess F.0000-0002-3174-5190
Additional Information:© 2016 Elsevier Ltd. Received Date: 1 December 2015; Accepted Date: 21 June 2016; Available online 25 June 2016. We are grateful to Nathan Dalleska, Fenfang Wu and Guillaume Paris (Caltech) for analytical assistance, and to Eric Tappa (U. of South Carolina) for assistance with samples. We also thank the US National Science Foundation (award OCE-1258991 to R.C.T.) and Fundación La Salle de Ciencias Naturales, Estación de Investigaciones Marinas Isla Margarita (FLASA/EDIMAR) for their continuous effort in maintaining the CARIACO Ocean Time-Series program. This work was supported by NSF Award #OCE-1529120 to A.L.S. and was also funded in part by the Gordon and Betty Moore Foundation through Grant GBMF#3306 to A.L.S. We are grateful for insightful comments from two anonymous reviewers that substantially improved the manuscript and for careful editorial handling by Joseph Werne.
Funding AgencyGrant Number
Gordon and Betty Moore FoundationGBMF 3306
Subject Keywords:Organic sulfur; Marine particulate organic matter (POM); Sulfur isotopes; Kerogen; Anoxic environments
Record Number:CaltechAUTHORS:20160714-073258113
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Official Citation:Morgan Reed Raven, Alex L. Sessions, Jess F. Adkins, Robert C. Thunell, Rapid organic matter sulfurization in sinking particles from the Cariaco Basin water column, Geochimica et Cosmochimica Acta, Volume 190, 1 October 2016, Pages 175-190, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:69016
Deposited By: Tony Diaz
Deposited On:27 Jul 2016 21:42
Last Modified:24 Feb 2020 10:30

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