Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments
<p>All hydrocarbon (HC) reservoirs leak to some extent. When small quantities of HCs escape offshore reservoirs and migrate through overlying organic-poor marine sediments towards the surface, these HCs are often completely metabolized by microorganisms before reaching the sediment–water inter...
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Copernicus Publications
2025-02-01
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| Series: | Biogeosciences |
| Online Access: | https://bg.copernicus.org/articles/22/767/2025/bg-22-767-2025.pdf |
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| author | E. Schnabel A. Vuillemin C. C. Laczny B. J. Kunath A. R. Soares A. J. Probst R. Di Primio J. Kallmeyer |
| author_facet | E. Schnabel A. Vuillemin C. C. Laczny B. J. Kunath A. R. Soares A. J. Probst R. Di Primio J. Kallmeyer |
| author_sort | E. Schnabel |
| collection | DOAJ |
| description | <p>All hydrocarbon (HC) reservoirs leak to some extent. When small quantities of HCs escape offshore reservoirs and migrate through overlying organic-poor marine sediments towards the surface, these HCs are often completely metabolized by microorganisms before reaching the sediment–water interface. However, these low and often unnoticed upward HC fluxes still influence the geochemistry of surrounding sediments and potentially stimulate metabolic activity by microbial populations in shallow subseafloor environments.</p>
<p>In this study, we examined how localized HC seepage affects microbial sulfate reduction in organic-poor sediments from the SW Barents Sea, focusing on three sampling areas overlying known HC deposits and two pristine seabed reference areas. The analysis of 50 gravity cores revealed significant variability in the predicted sulfate depletion depth, ranging from 3 to 12 m below the seafloor. We observed nearly linear pore water sulfate and alkalinity profiles, alongside low rates of sulfate reduction (pmol cm<span class="inline-formula"><sup>3</sup></span> d<span class="inline-formula"><sup>−1</sup></span>). Metagenomic and metatranscriptomic data indicated metabolic potential and activity towards sulfate reduction and anaerobic oxidation of methane (AOM). Expression of functional marker genes (<i>aprAB</i>, <i>dsrAB</i>, <i>mcrA</i>) revealed metabolic activities by sulfate-reducing Desulfobacterota and methanotrophic ANME-1 archaea sustained by HC traces in the sediment. Furthermore, in concomitance to AOM processes, we found that archaea amongst the classes Lokiarchaeia and Thorarchaeia were expressing genes involved in sulfur reduction (<i>hydB, hydG</i>).</p>
<p>Overall, our study demonstrates that the gradient in pore water geochemistry, the rates of sulfate reduction processes, and the genetic features of microbial populations actively involved in sulfate-driven AOM processes are all affected by low and often unnoticed upward HC fluxes. This slight HC seepage resulted in sulfate depletion at shallower depths compared to what would be expected at a comparable non-affected site and produced concomitant biogeochemical signatures in the shallow subsurface that enable the inference of deeply buried reservoirs.</p> |
| format | Article |
| id | doaj-art-2dd534cabc3b4c19aec63eebc69c2857 |
| institution | Kabale University |
| issn | 1726-4170 1726-4189 |
| language | English |
| publishDate | 2025-02-01 |
| publisher | Copernicus Publications |
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| series | Biogeosciences |
| spelling | doaj-art-2dd534cabc3b4c19aec63eebc69c28572025-02-12T07:11:13ZengCopernicus PublicationsBiogeosciences1726-41701726-41892025-02-012276778410.5194/bg-22-767-2025Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sedimentsE. Schnabel0A. Vuillemin1C. C. Laczny2B. J. Kunath3A. R. Soares4A. J. Probst5R. Di Primio6J. Kallmeyer7GFZ Helmholtz Centre for Geosciences, Section Geomicrobiology, Telegrafenberg, 14473 Potsdam, GermanyGFZ Helmholtz Centre for Geosciences, Section Geomicrobiology, Telegrafenberg, 14473 Potsdam, GermanyLuxembourg Centre for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, LuxembourgLuxembourg Centre for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, LuxembourgEnvironmental Metagenomics, Research Center One Health Ruhr of the University Alliance Ruhr, Faculty of Chemistry, University of Duisburg–Essen, Essen, GermanyEnvironmental Metagenomics, Research Center One Health Ruhr of the University Alliance Ruhr, Faculty of Chemistry, University of Duisburg–Essen, Essen, GermanyAkerBP, 1366 Lysaker, NorwayGFZ Helmholtz Centre for Geosciences, Section Geomicrobiology, Telegrafenberg, 14473 Potsdam, Germany<p>All hydrocarbon (HC) reservoirs leak to some extent. When small quantities of HCs escape offshore reservoirs and migrate through overlying organic-poor marine sediments towards the surface, these HCs are often completely metabolized by microorganisms before reaching the sediment–water interface. However, these low and often unnoticed upward HC fluxes still influence the geochemistry of surrounding sediments and potentially stimulate metabolic activity by microbial populations in shallow subseafloor environments.</p> <p>In this study, we examined how localized HC seepage affects microbial sulfate reduction in organic-poor sediments from the SW Barents Sea, focusing on three sampling areas overlying known HC deposits and two pristine seabed reference areas. The analysis of 50 gravity cores revealed significant variability in the predicted sulfate depletion depth, ranging from 3 to 12 m below the seafloor. We observed nearly linear pore water sulfate and alkalinity profiles, alongside low rates of sulfate reduction (pmol cm<span class="inline-formula"><sup>3</sup></span> d<span class="inline-formula"><sup>−1</sup></span>). Metagenomic and metatranscriptomic data indicated metabolic potential and activity towards sulfate reduction and anaerobic oxidation of methane (AOM). Expression of functional marker genes (<i>aprAB</i>, <i>dsrAB</i>, <i>mcrA</i>) revealed metabolic activities by sulfate-reducing Desulfobacterota and methanotrophic ANME-1 archaea sustained by HC traces in the sediment. Furthermore, in concomitance to AOM processes, we found that archaea amongst the classes Lokiarchaeia and Thorarchaeia were expressing genes involved in sulfur reduction (<i>hydB, hydG</i>).</p> <p>Overall, our study demonstrates that the gradient in pore water geochemistry, the rates of sulfate reduction processes, and the genetic features of microbial populations actively involved in sulfate-driven AOM processes are all affected by low and often unnoticed upward HC fluxes. This slight HC seepage resulted in sulfate depletion at shallower depths compared to what would be expected at a comparable non-affected site and produced concomitant biogeochemical signatures in the shallow subsurface that enable the inference of deeply buried reservoirs.</p>https://bg.copernicus.org/articles/22/767/2025/bg-22-767-2025.pdf |
| spellingShingle | E. Schnabel A. Vuillemin C. C. Laczny B. J. Kunath A. R. Soares A. J. Probst R. Di Primio J. Kallmeyer Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments Biogeosciences |
| title | Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments |
| title_full | Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments |
| title_fullStr | Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments |
| title_full_unstemmed | Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments |
| title_short | Influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments |
| title_sort | influence of minor hydrocarbon seepage on sulfur cycling in marine subsurface sediments |
| url | https://bg.copernicus.org/articles/22/767/2025/bg-22-767-2025.pdf |
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