Production and preservation of organic carbon in sub-seafloor tephra layers
Production and preservation of organic carbon in sub-seafloor tephra layers
The deposition of volcanic ash into the ocean initiates a range of chemical and biological reactions. During diagenesis, these reactions may enhance the preservation of organic carbon (OC) in marine sediments, which ultimately promotes CO2 sequestration from the ocean-atmosphere system. However, this interpretation is reliant on a small number of studies that make a link between tephra and OC burial. Here, we compare organic and inorganic geochemical data from tephra-bearing marine sediments from three sites that differ widely in their location, age, and composition. We show that OC is buried in, and proximal to, tephra layers, in proportions higher than would be expected via simple admixture of surrounding sediment. Our data indicate that this OC is preserved primarily through interactions with reactive iron phases, which act to physically protect the carbon from oxidation. Analysis of the composition of the OC associated with reactive iron indicates it is isotopically (consistently more negative δ13C than sediment) and chemically (comprised of compounds not found in the sediment) distinct from OC in the background sediments. We interpret this signal as indicating a microbial source of OC, with autochthonous OC production resulting from autotrophic microbial exploitation of nutrients supplied from tephra. This finding has implications for our understanding of carbon cycling on Earth, and possibly for the emergence of life in terrestrial and perhaps even extra-terrestrial environments.
Autotrophy, Marine sediment, Microbial carbon, Organic carbon, Tephra
Longman, Jack
669ddb44-2016-4e6d-b3cf-cb5477461fc1
Manners, Hayley R.
f9e36f04-096a-4e2c-9617-c506e0cf3acd
Gernon, Thomas M.
658041a0-fdd1-4516-85f4-98895a39235e
McManus, James
aa7cdfbc-6cf6-4bd8-b2b4-d3bf72fce647
Palmer, Martin R.
d2e60e81-5d6e-4ddb-a243-602537286080
Rowland, Steven J.
ba619e64-7494-4f53-9a5f-e9c63d71e094
Sutton, Paul A.
3d239c9b-ff7a-4d42-849c-9805af01e411
January 2024
Longman, Jack
669ddb44-2016-4e6d-b3cf-cb5477461fc1
Manners, Hayley R.
f9e36f04-096a-4e2c-9617-c506e0cf3acd
Gernon, Thomas M.
658041a0-fdd1-4516-85f4-98895a39235e
McManus, James
aa7cdfbc-6cf6-4bd8-b2b4-d3bf72fce647
Palmer, Martin R.
d2e60e81-5d6e-4ddb-a243-602537286080
Rowland, Steven J.
ba619e64-7494-4f53-9a5f-e9c63d71e094
Sutton, Paul A.
3d239c9b-ff7a-4d42-849c-9805af01e411
Longman, Jack, Manners, Hayley R., Gernon, Thomas M., McManus, James, Palmer, Martin R., Rowland, Steven J. and Sutton, Paul A.
(2024)
Production and preservation of organic carbon in sub-seafloor tephra layers.
Marine Chemistry, 258, [104334].
(doi:10.1016/j.marchem.2023.104334).
Abstract
The deposition of volcanic ash into the ocean initiates a range of chemical and biological reactions. During diagenesis, these reactions may enhance the preservation of organic carbon (OC) in marine sediments, which ultimately promotes CO2 sequestration from the ocean-atmosphere system. However, this interpretation is reliant on a small number of studies that make a link between tephra and OC burial. Here, we compare organic and inorganic geochemical data from tephra-bearing marine sediments from three sites that differ widely in their location, age, and composition. We show that OC is buried in, and proximal to, tephra layers, in proportions higher than would be expected via simple admixture of surrounding sediment. Our data indicate that this OC is preserved primarily through interactions with reactive iron phases, which act to physically protect the carbon from oxidation. Analysis of the composition of the OC associated with reactive iron indicates it is isotopically (consistently more negative δ13C than sediment) and chemically (comprised of compounds not found in the sediment) distinct from OC in the background sediments. We interpret this signal as indicating a microbial source of OC, with autochthonous OC production resulting from autotrophic microbial exploitation of nutrients supplied from tephra. This finding has implications for our understanding of carbon cycling on Earth, and possibly for the emergence of life in terrestrial and perhaps even extra-terrestrial environments.
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Accepted/In Press date: 16 November 2023
e-pub ahead of print date: 23 November 2023
Published date: January 2024
Additional Information:
Funding Information:
Funding for this research was provided by NERC grant NE/K00543X/1 to Gernon and Palmer and the US National Science Foundation under grant numbers 1360077 and 1715106 to McManus. We are indebted to A. Tonkin for providing knowledge and experience in CHN analysis at Plymouth University, UK and A. Hartwell at the University of Akron, USA for assistance with the reactive metal analyses. We also thank the staff at the IODP core repository Bremen, the IODP Kochi Core Centre (KCC) Japan, and the IODP Gulf Coast Core Repository (GCR) at Texas A&M University, for assistance with sampling. We are grateful for input of the reviewers, whose comments helpe dus to improve the paper.
Funding Information:
Funding for this research was provided by NERC grant NE/K00543X/1 to Gernon and Palmer and the US National Science Foundation under grant numbers 1360077 and 1715106 to McManus. We are indebted to A. Tonkin for providing knowledge and experience in CHN analysis at Plymouth University, UK and A. Hartwell at the University of Akron, USA for assistance with the reactive metal analyses. We also thank the staff at the IODP core repository Bremen, the IODP Kochi Core Centre (KCC) Japan, and the IODP Gulf Coast Core Repository (GCR) at Texas A&M University, for assistance with sampling. We are grateful for input of the reviewers, whose comments helpe dus to improve the paper.
Publisher Copyright:
© 2023 The Authors
Keywords:
Autotrophy, Marine sediment, Microbial carbon, Organic carbon, Tephra
Identifiers
Local EPrints ID: 485501
URI: http://eprints.soton.ac.uk/id/eprint/485501
ISSN: 0304-4203
PURE UUID: 60769f86-587a-4df0-854a-dd45518431cd
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Date deposited: 07 Dec 2023 17:37
Last modified: 18 Mar 2024 03:15
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Contributors
Author:
Jack Longman
Author:
Hayley R. Manners
Author:
James McManus
Author:
Steven J. Rowland
Author:
Paul A. Sutton
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