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Geochemistry, faunal composition and trophic structure in reducing sediments on the South West South Georgia margin

Geochemistry, faunal composition and trophic structure in reducing sediments on the South West South Georgia margin
Geochemistry, faunal composition and trophic structure in reducing sediments on the South West South Georgia margin
Despite a number of studies in areas of focused methane seepage, the extent of transitional sediments of more diffuse methane seepage, and their influence upon biological communities is poorly understood. We investigated an area of reducing sediments with elevated levels of methane on the South Georgia margin around 250?m depth and report data from a series of geochemical and biological analyses. Here, the geochemical signatures were consistent with weak methane seepage and the role of sub-surface methane consumption was clearly very important, preventing gas emissions into bottom waters. As a result, the contribution of methane-derived carbon to the microbial and metazoan food webs was very limited, although sulfur isotopic signatures indicated a wider range of dietary contributions than was apparent from carbon isotope ratios. Macrofaunal assemblages had high dominance and were indicative of reducing sediments, with many taxa common to other similar environments and no seep-endemic fauna, indicating transitional assemblages. Also similar to other cold seep areas, there were samples of authigenic carbonate, but rather than occurring as pavements or sedimentary concretions, these carbonates were restricted to patches on the shells of Axinulus antarcticus (Bivalvia, Thyasiridae), which is suggestive of microbe–metazoan interactions.
160284
Bell, James B.
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Aquilina, Alfred
a5ce0174-e2d4-40ee-baa5-86ba2f24058c
Woulds, Clare
58a10ca2-cb85-449b-ba50-deb48d9a12d4
Glover, Adrian G.
91192a3a-fc25-4c1f-b062-2e4da183272e
Little, Crispin T.S.
34fb970d-b495-4d6a-8e2e-5161319d4bdd
Reid, William D.K.
40d8b78a-635c-4bba-a861-d64d5d4daefe
Hepburn, Laura E.
081962e4-718a-4158-9311-9effd96bbf86
Newton, Jason
0d986c1e-4ecf-4854-aced-0197cf446ce0
Mills, Rachel A.
a664f299-1a34-4b63-9988-1e599b756706
Bell, James B.
74cdb23e-5474-431d-952c-96e87392987a
Aquilina, Alfred
a5ce0174-e2d4-40ee-baa5-86ba2f24058c
Woulds, Clare
58a10ca2-cb85-449b-ba50-deb48d9a12d4
Glover, Adrian G.
91192a3a-fc25-4c1f-b062-2e4da183272e
Little, Crispin T.S.
34fb970d-b495-4d6a-8e2e-5161319d4bdd
Reid, William D.K.
40d8b78a-635c-4bba-a861-d64d5d4daefe
Hepburn, Laura E.
081962e4-718a-4158-9311-9effd96bbf86
Newton, Jason
0d986c1e-4ecf-4854-aced-0197cf446ce0
Mills, Rachel A.
a664f299-1a34-4b63-9988-1e599b756706

Bell, James B., Aquilina, Alfred, Woulds, Clare, Glover, Adrian G., Little, Crispin T.S., Reid, William D.K., Hepburn, Laura E., Newton, Jason and Mills, Rachel A. (2016) Geochemistry, faunal composition and trophic structure in reducing sediments on the South West South Georgia margin. Royal Society Open Science, 3 (9), 160284. (doi:10.1098/rsos.160284).

Record type: Article

Abstract

Despite a number of studies in areas of focused methane seepage, the extent of transitional sediments of more diffuse methane seepage, and their influence upon biological communities is poorly understood. We investigated an area of reducing sediments with elevated levels of methane on the South Georgia margin around 250?m depth and report data from a series of geochemical and biological analyses. Here, the geochemical signatures were consistent with weak methane seepage and the role of sub-surface methane consumption was clearly very important, preventing gas emissions into bottom waters. As a result, the contribution of methane-derived carbon to the microbial and metazoan food webs was very limited, although sulfur isotopic signatures indicated a wider range of dietary contributions than was apparent from carbon isotope ratios. Macrofaunal assemblages had high dominance and were indicative of reducing sediments, with many taxa common to other similar environments and no seep-endemic fauna, indicating transitional assemblages. Also similar to other cold seep areas, there were samples of authigenic carbonate, but rather than occurring as pavements or sedimentary concretions, these carbonates were restricted to patches on the shells of Axinulus antarcticus (Bivalvia, Thyasiridae), which is suggestive of microbe–metazoan interactions.

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Accepted/In Press date: 25 August 2016
e-pub ahead of print date: 28 September 2016
Published date: 28 September 2016
Organisations: Geochemistry

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Local EPrints ID: 401940
URI: https://eprints.soton.ac.uk/id/eprint/401940
PURE UUID: 08083516-f5e3-48ae-b718-d24496526859
ORCID for Rachel A. Mills: ORCID iD orcid.org/0000-0002-9811-246X

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Date deposited: 24 Oct 2016 08:46
Last modified: 15 Aug 2019 00:54

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Contributors

Author: James B. Bell
Author: Alfred Aquilina
Author: Clare Woulds
Author: Adrian G. Glover
Author: Crispin T.S. Little
Author: William D.K. Reid
Author: Laura E. Hepburn
Author: Jason Newton
Author: Rachel A. Mills ORCID iD

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