Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge
<p>We report a rare observation of a mini-fracture in near-surface sediments (30 cm below the seafloor) visualized using a rotational scanning X-ray of a core recovered from the Lomvi pockmark, Vestnesa Ridge, west of Svalbard (1200 m water depth). Porewater geochemistry...
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Format: | Article |
Language: | English |
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Copernicus Publications
2019-05-01
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Series: | Biogeosciences |
Online Access: | https://www.biogeosciences.net/16/2221/2019/bg-16-2221-2019.pdf |
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record_format |
Article |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
H. Yao W.-L. Hong W.-L. Hong G. Panieri S. Sauer S. Sauer M. E. Torres M. F. Lehmann F. Gründger H. Niemann H. Niemann H. Niemann H. Niemann |
spellingShingle |
H. Yao W.-L. Hong W.-L. Hong G. Panieri S. Sauer S. Sauer M. E. Torres M. F. Lehmann F. Gründger H. Niemann H. Niemann H. Niemann H. Niemann Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge Biogeosciences |
author_facet |
H. Yao W.-L. Hong W.-L. Hong G. Panieri S. Sauer S. Sauer M. E. Torres M. F. Lehmann F. Gründger H. Niemann H. Niemann H. Niemann H. Niemann |
author_sort |
H. Yao |
title |
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge |
title_short |
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge |
title_full |
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge |
title_fullStr |
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge |
title_full_unstemmed |
Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa Ridge |
title_sort |
fracture-controlled fluid transport supports microbial methane-oxidizing communities at vestnesa ridge |
publisher |
Copernicus Publications |
series |
Biogeosciences |
issn |
1726-4170 1726-4189 |
publishDate |
2019-05-01 |
description |
<p>We report a rare observation of a mini-fracture in near-surface
sediments (30 cm below the seafloor) visualized using a rotational scanning
X-ray of a core recovered from the Lomvi pockmark, Vestnesa Ridge, west of
Svalbard (1200 m water depth). Porewater geochemistry and lipid biomarker
signatures revealed clear differences in the geochemical and biogeochemical
regimes of this core compared with two additional unfractured cores
recovered from pockmark sites at Vestnesa Ridge, which we attribute to
differential methane transport mechanisms. In the sediment core featuring
the shallow mini-fracture at pockmark Lomvi, we observed high concentrations
of both methane and sulfate throughout the core in tandem with moderately
elevated values for total alkalinity, <span class="inline-formula"><sup>13</sup>C</span>-depleted dissolved inorganic
carbon (DIC), and <span class="inline-formula"><sup>13</sup>C</span>-depleted lipid biomarkers (diagnostic for the
slow-growing microbial communities mediating the anaerobic oxidation of
methane with sulfate – AOM). In a separate unfractured core, recovered from
the same pockmark about 80 m away from the fractured core, we observed
complete sulfate depletion in the top centimeters of the sediment and much
more pronounced signatures of AOM than in the fractured core. Our data
indicate a gas advection-dominated transport mode in both cores, facilitating
methane migration into sulfate-rich surface sediments. However, the moderate
expression of AOM signals suggest a rather recent onset of gas migration at
the site of the fractured core, while the geochemical evidence for a
well-established AOM community at the second coring site suggest that gas
migration has been going on for a longer period of time. A third core
recovered from another pockmark along the Vestnesa Ridge Lunde pockmark
was dominated by diffusive transport with only weak geochemical and
biogeochemical evidence for AOM. Our study highlights that advective fluid
and gas transport supported by mini-fractures can be important in modulating
methane dynamics in surface sediments.</p> |
url |
https://www.biogeosciences.net/16/2221/2019/bg-16-2221-2019.pdf |
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doaj-74816df4d4b3456482851b09744e2a3b2020-11-25T01:22:58ZengCopernicus PublicationsBiogeosciences1726-41701726-41892019-05-01162221223210.5194/bg-16-2221-2019Fracture-controlled fluid transport supports microbial methane-oxidizing communities at Vestnesa RidgeH. Yao0W.-L. Hong1W.-L. Hong2G. Panieri3S. Sauer4S. Sauer5M. E. Torres6M. F. Lehmann7F. Gründger8H. Niemann9H. Niemann10H. Niemann11H. Niemann12Centre for Arctic Gas Hydrate (CAGE), Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway in Tromsø, Tromsø, NorwayCentre for Arctic Gas Hydrate (CAGE), Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway in Tromsø, Tromsø, NorwayGeological Survey of Norway (NGU), Trondheim, NorwayCentre for Arctic Gas Hydrate (CAGE), Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway in Tromsø, Tromsø, NorwayCentre for Arctic Gas Hydrate (CAGE), Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway in Tromsø, Tromsø, NorwayGeological Survey of Norway (NGU), Trondheim, NorwayCollege of Earth, Ocean, and Atmospheric Sciences (CEOAS), Oregon State University, Corvallis, USADepartment of Environmental Sciences, University of Basel, Basel, SwitzerlandCentre for Arctic Gas Hydrate (CAGE), Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway in Tromsø, Tromsø, NorwayCentre for Arctic Gas Hydrate (CAGE), Environment and Climate, Department of Geosciences, UiT The Arctic University of Norway in Tromsø, Tromsø, NorwayDepartment of Environmental Sciences, University of Basel, Basel, SwitzerlandRoyal Netherlands Institute for Sea Research (NIOZ), Department of Marine Microbiology and Biogeochemistry, and Utrecht University, den Burg, the NetherlandsDepartment of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, the Netherlands<p>We report a rare observation of a mini-fracture in near-surface sediments (30 cm below the seafloor) visualized using a rotational scanning X-ray of a core recovered from the Lomvi pockmark, Vestnesa Ridge, west of Svalbard (1200 m water depth). Porewater geochemistry and lipid biomarker signatures revealed clear differences in the geochemical and biogeochemical regimes of this core compared with two additional unfractured cores recovered from pockmark sites at Vestnesa Ridge, which we attribute to differential methane transport mechanisms. In the sediment core featuring the shallow mini-fracture at pockmark Lomvi, we observed high concentrations of both methane and sulfate throughout the core in tandem with moderately elevated values for total alkalinity, <span class="inline-formula"><sup>13</sup>C</span>-depleted dissolved inorganic carbon (DIC), and <span class="inline-formula"><sup>13</sup>C</span>-depleted lipid biomarkers (diagnostic for the slow-growing microbial communities mediating the anaerobic oxidation of methane with sulfate – AOM). In a separate unfractured core, recovered from the same pockmark about 80 m away from the fractured core, we observed complete sulfate depletion in the top centimeters of the sediment and much more pronounced signatures of AOM than in the fractured core. Our data indicate a gas advection-dominated transport mode in both cores, facilitating methane migration into sulfate-rich surface sediments. However, the moderate expression of AOM signals suggest a rather recent onset of gas migration at the site of the fractured core, while the geochemical evidence for a well-established AOM community at the second coring site suggest that gas migration has been going on for a longer period of time. A third core recovered from another pockmark along the Vestnesa Ridge Lunde pockmark was dominated by diffusive transport with only weak geochemical and biogeochemical evidence for AOM. Our study highlights that advective fluid and gas transport supported by mini-fractures can be important in modulating methane dynamics in surface sediments.</p>https://www.biogeosciences.net/16/2221/2019/bg-16-2221-2019.pdf |