Suspended particles are hotspots of microbial remineralization in the ocean's twilight zone
Suspended particles are hotspots of microbial remineralization in the ocean's twilight zone
The sinking of photosynthetically produced organic carbon from the ocean surface to its interior is a significant term in the global carbon cycle. Most sinking organic carbon is, however, remineralized in the mesopelagic zone (∼100 m–1000 m), thereby exerting control over ocean-atmosphere carbon dioxide (CO2) partitioning and hence global climate. Sinking particles are considered hotspots of microbial respiration in the dark ocean. However, our observations in the contrasting Scotia Sea and the Benguela Current show that >90% of microbial remineralisation is associated with suspended, rather than sinking, organic matter, resulting in rapid turnover of the suspended carbon pool and demonstrating its central role in mesopelagic carbon cycling. A non-steady-state model indicates that temporally variable particle fluxes, particle injection pumps and local chemoautotrophy are necessary to help balance the observed mesopelagic respiration. Temperature and oxygen exert control over microbial respiration, particularly for the suspended fraction, further demonstrating the susceptibility of microbial remineralisation to the ongoing decline in oxygen at mid-ocean depths. These observations suggest a partial decoupling of carbon cycling between non-sinking and fast-sinking organic matter, challenging our understanding of how oceanic biological processes regulate climate.
Carbon cycling, Chemoautotrophic, Dissolved organic matter, Microbial respiration, Suspended particles
Hemsley, V.
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Füssel, J.
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Duret, M.T.
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Rayne, R.R.
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Iversen, M.H.
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Henson, S.A.
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Sanders, R.
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Lam, P.
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Trimmer, M.
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22 October 2023
Hemsley, V.
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Füssel, J.
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Duret, M.T.
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Rayne, R.R.
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Iversen, M.H.
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Henson, S.A.
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Sanders, R.
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Lam, P.
996aef80-a15d-4827-aed8-1b97b378f6ad
Trimmer, M.
4ee1556e-227e-4283-ae5a-be06be73691b
Hemsley, V., Füssel, J., Duret, M.T., Rayne, R.R., Iversen, M.H., Henson, S.A., Sanders, R., Lam, P. and Trimmer, M.
(2023)
Suspended particles are hotspots of microbial remineralization in the ocean's twilight zone.
Deep-Sea Research Part II: Topical Studies in Oceanography, 212, [105339].
(doi:10.1016/j.dsr2.2023.105339).
Abstract
The sinking of photosynthetically produced organic carbon from the ocean surface to its interior is a significant term in the global carbon cycle. Most sinking organic carbon is, however, remineralized in the mesopelagic zone (∼100 m–1000 m), thereby exerting control over ocean-atmosphere carbon dioxide (CO2) partitioning and hence global climate. Sinking particles are considered hotspots of microbial respiration in the dark ocean. However, our observations in the contrasting Scotia Sea and the Benguela Current show that >90% of microbial remineralisation is associated with suspended, rather than sinking, organic matter, resulting in rapid turnover of the suspended carbon pool and demonstrating its central role in mesopelagic carbon cycling. A non-steady-state model indicates that temporally variable particle fluxes, particle injection pumps and local chemoautotrophy are necessary to help balance the observed mesopelagic respiration. Temperature and oxygen exert control over microbial respiration, particularly for the suspended fraction, further demonstrating the susceptibility of microbial remineralisation to the ongoing decline in oxygen at mid-ocean depths. These observations suggest a partial decoupling of carbon cycling between non-sinking and fast-sinking organic matter, challenging our understanding of how oceanic biological processes regulate climate.
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Accepted/In Press date: 30 September 2023
e-pub ahead of print date: 12 October 2023
Published date: 22 October 2023
Additional Information:
Funding Information:
This work was conducted as part of the collaborative research project “Controls over Ocean mesopelagic Interior Carbon Storage (COMICS)” (NE/M020835/2 to RS and SAH, NE/M020908/1 to MT and NE/M02072X/1 to PL). This work was also supported by a European Research Council Consolidator grant (GOCART, agreement number 724416) to SAH. We sincerely thank the captains and the crews of the RRS Discovery (cruise DY086 and DY090) for their support at sea. We are grateful for the technical and analytical assistance of Ian Sanders (Queen Mary University of London), Mark Stinchcombe (National Oceanography Centre Southampton) and Cynthia Dumousseaud (University of Southampton). We are grateful to the staff of Logistics and Warehousing (National Oceanography Centre Southampton) for logistical support. For fruitful scientific discussions we would like to acknowledge Richard Lampitt and Nathan Briggs (National Oceanography Centre Southampton).
Funding Information:
This work was conducted as part of the collaborative research project “Controls over Ocean mesopelagic Interior Carbon Storage (COMICS)” (NE/M020835/2 to RS and SAH, NE/M020908/1 to MT and NE/M02072X/1 to PL). This work was also supported by a European Research Council Consolidator grant (GOCART, agreement number 724416) to SAH. We sincerely thank the captains and the crews of the RRS Discovery (cruise DY086 and DY090) for their support at sea. We are grateful for the technical and analytical assistance of Ian Sanders (Queen Mary University of London), Mark Stinchcombe (National Oceanography Centre Southampton) and Cynthia Dumousseaud (University of Southampton). We are grateful to the staff of Logistics and Warehousing (National Oceanography Centre Southampton) for logistical support. For fruitful scientific discussions we would like to acknowledge Richard Lampitt and Nathan Briggs (National Oceanography Centre Southampton).
Keywords:
Carbon cycling, Chemoautotrophic, Dissolved organic matter, Microbial respiration, Suspended particles
Identifiers
Local EPrints ID: 483675
URI: http://eprints.soton.ac.uk/id/eprint/483675
ISSN: 0967-0645
PURE UUID: 69a270dc-afe3-4324-8c74-84d26fabf6c2
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Date deposited: 03 Nov 2023 17:50
Last modified: 27 Apr 2024 01:50
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Contributors
Author:
V. Hemsley
Author:
J. Füssel
Author:
M.T. Duret
Author:
M.H. Iversen
Author:
R. Sanders
Author:
M. Trimmer
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