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Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation

Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation
Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation
Oceanic dissolved organic carbon (DOC) is an important carbon pool, similar in magnitude to atmospheric CO2, but the fate of its oldest forms is not well understood. Hot hydrothermal circulation may facilitate the degradation of otherwise un-reactive dissolved organic matter, playing an important role in the long-term global carbon cycle. The oldest, most recalcitrant forms of DOC, which make up most of oceanic DOC, can be recovered by solid-phase extraction. Here we present measurements of solid-phase extractable DOC from samples collected between 2009 and 2013 at seven vent sites in the Atlantic, Pacific and Southern oceans, along with magnesium concentrations, a conservative tracer of water circulation through hydrothermal systems. We find that magnesium and solid-phase extractable DOC concentrations are correlated, suggesting that solid-phase extractable DOC is almost entirely lost from solution through mineralization or deposition during circulation through hydrothermal vents with fluid temperatures of 212–401?°C. In laboratory experiments, where we heated samples to 380?°C for four days, we found a similar removal efficiency. We conclude that thermal degradation alone can account for the loss of solid-phase extractable DOC in natural hydrothermal systems, and that its maximum lifetime is constrained by the timescale of hydrothermal cycling, at about 40 million years.
1752-0894
856-860
Hawkes, Jeffrey A.
19e298a9-b5bf-4987-bfea-07780ca5bd69
Rossel, Pamela E.
c655b01b-bd3d-4059-8cee-1a57c58e1aee
Stubbins, Aron
8993eaac-c361-4c6d-876f-25aa49a45af6
Butterfield, David
b57b8011-aef9-4f54-9be2-f59c4c3c4544
Connelly, Douglas P.
d49131bb-af38-4768-9953-7ae0b43e33c8
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Koschinsky, Andrea
60c88616-530f-40d8-9c4c-658cb08aed65
Chavagnac, Valérie
2beb897f-660c-4a91-a57e-16a05a638dc8
Hansen, Christian T.
7d271ab2-88e4-445d-8ba1-fce4d21c8b22
Bach, Wolfgang
aca0e0cb-1830-43bc-8410-e50a1e392b8a
Dittmar, Thorsten
38cc8f62-b49f-402c-a3d1-1b95cae4ec56
Hawkes, Jeffrey A.
19e298a9-b5bf-4987-bfea-07780ca5bd69
Rossel, Pamela E.
c655b01b-bd3d-4059-8cee-1a57c58e1aee
Stubbins, Aron
8993eaac-c361-4c6d-876f-25aa49a45af6
Butterfield, David
b57b8011-aef9-4f54-9be2-f59c4c3c4544
Connelly, Douglas P.
d49131bb-af38-4768-9953-7ae0b43e33c8
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Koschinsky, Andrea
60c88616-530f-40d8-9c4c-658cb08aed65
Chavagnac, Valérie
2beb897f-660c-4a91-a57e-16a05a638dc8
Hansen, Christian T.
7d271ab2-88e4-445d-8ba1-fce4d21c8b22
Bach, Wolfgang
aca0e0cb-1830-43bc-8410-e50a1e392b8a
Dittmar, Thorsten
38cc8f62-b49f-402c-a3d1-1b95cae4ec56

Hawkes, Jeffrey A., Rossel, Pamela E., Stubbins, Aron, Butterfield, David, Connelly, Douglas P., Achterberg, Eric P., Koschinsky, Andrea, Chavagnac, Valérie, Hansen, Christian T., Bach, Wolfgang and Dittmar, Thorsten (2015) Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation. Nature Geoscience, 8 (11), 856-860. (doi:10.1038/ngeo2543).

Record type: Article

Abstract

Oceanic dissolved organic carbon (DOC) is an important carbon pool, similar in magnitude to atmospheric CO2, but the fate of its oldest forms is not well understood. Hot hydrothermal circulation may facilitate the degradation of otherwise un-reactive dissolved organic matter, playing an important role in the long-term global carbon cycle. The oldest, most recalcitrant forms of DOC, which make up most of oceanic DOC, can be recovered by solid-phase extraction. Here we present measurements of solid-phase extractable DOC from samples collected between 2009 and 2013 at seven vent sites in the Atlantic, Pacific and Southern oceans, along with magnesium concentrations, a conservative tracer of water circulation through hydrothermal systems. We find that magnesium and solid-phase extractable DOC concentrations are correlated, suggesting that solid-phase extractable DOC is almost entirely lost from solution through mineralization or deposition during circulation through hydrothermal vents with fluid temperatures of 212–401?°C. In laboratory experiments, where we heated samples to 380?°C for four days, we found a similar removal efficiency. We conclude that thermal degradation alone can account for the loss of solid-phase extractable DOC in natural hydrothermal systems, and that its maximum lifetime is constrained by the timescale of hydrothermal cycling, at about 40 million years.

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e-pub ahead of print date: 28 September 2015
Published date: November 2015
Organisations: Ocean and Earth Science, Marine Geoscience

Identifiers

Local EPrints ID: 384720
URI: http://eprints.soton.ac.uk/id/eprint/384720
ISSN: 1752-0894
PURE UUID: 1ea557ac-bd0c-4cd9-b9aa-8aaa573f30f8

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Date deposited: 02 Dec 2015 09:49
Last modified: 09 Jan 2022 04:50

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Contributors

Author: Jeffrey A. Hawkes
Author: Pamela E. Rossel
Author: Aron Stubbins
Author: David Butterfield
Author: Douglas P. Connelly
Author: Andrea Koschinsky
Author: Valérie Chavagnac
Author: Christian T. Hansen
Author: Wolfgang Bach
Author: Thorsten Dittmar

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