ORCID

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.

Publication Date

2024-01-01

Publication Title

Marine Chemistry

Volume

258

ISSN

1872-7581

Acceptance Date

2023-11-16

Deposit Date

2023-11-17

Embargo Period

2023-12-06

Funding

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 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.

Keywords

Autotrophy, Marine sediment, Microbial carbon, Organic carbon, Tephra

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