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Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low particulate organic carbon flux region of the eastern Pacific Ocean

Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low particulate organic carbon flux region of the eastern Pacific Ocean
Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low particulate organic carbon flux region of the eastern Pacific Ocean

The cycling of carbon (C) by benthic organisms is a key ecosystem function in the deep sea. Pulse-chase experiments are designed to quantify this process, yet few studies have been carried out using abyssal (3500–6000 m) sediments and only a handful of studies have been undertaken in situ. We undertook eight in situ pulse-chase experiments in three abyssal strata (4050–4200 m water depth) separated by tens to hundreds of kilometers in the eastern Clarion-Clipperton Fracture Zone (CCFZ). These experiments demonstrated that benthic bacteria dominated the consumption of phytodetritus over short (~ 1.5 d) time scales, with metazoan macrofauna playing a minor role. These results contrast with the only other comparable in situ abyssal study, where macrofauna dominated phytodetritus assimilation over short (2.5 d) time scales in the eutrophic NE Atlantic. We also demonstrated that benthic bacteria were capable of converting dissolved inorganic C into biomass and showed that this process can occur at rates that are as high as the bacterial assimilation of algal-derived organic C. This demonstrates the potential importance of inorganic C uptake to abyssal ecosystems in this region. It also alludes to the possibility that some of the C incorporation by bacteria in our algal-addition studies may have resulted from the incorporation of labeled dissolved inorganic carbon initially respired by other unstudied organisms. Our findings reveal the key importance of benthic bacteria in the short-term cycling of C in abyssal habitats in the eastern CCFZ and provide important information on benthic ecosystem functioning in an area targeted for commercial-scale, deep-sea mining activities.

0024-3590
694-713
Sweetman, Andrew K.
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Smith, Craig R.
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Shulse, Christine N.
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Maillot, Brianne
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Lindh, Markus
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Church, Matthew J.
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Meyer, Kirstin S.
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van Oevelen, Dick
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Stratmann, Tanja
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Gooday, Andrew J.
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Sweetman, Andrew K.
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Smith, Craig R.
a99f491d-b292-47c1-9f16-3cde8f85bc0d
Shulse, Christine N.
54add35a-2fe5-4700-a08a-4fceade11391
Maillot, Brianne
56125ed9-bd7e-470c-969d-a14091464e33
Lindh, Markus
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Church, Matthew J.
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Meyer, Kirstin S.
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van Oevelen, Dick
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Stratmann, Tanja
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Gooday, Andrew J.
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Sweetman, Andrew K., Smith, Craig R., Shulse, Christine N., Maillot, Brianne, Lindh, Markus, Church, Matthew J., Meyer, Kirstin S., van Oevelen, Dick, Stratmann, Tanja and Gooday, Andrew J. (2019) Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low particulate organic carbon flux region of the eastern Pacific Ocean. Limnology and Oceanography, 64 (2), 694-713. (doi:10.1002/lno.11069).

Record type: Article

Abstract

The cycling of carbon (C) by benthic organisms is a key ecosystem function in the deep sea. Pulse-chase experiments are designed to quantify this process, yet few studies have been carried out using abyssal (3500–6000 m) sediments and only a handful of studies have been undertaken in situ. We undertook eight in situ pulse-chase experiments in three abyssal strata (4050–4200 m water depth) separated by tens to hundreds of kilometers in the eastern Clarion-Clipperton Fracture Zone (CCFZ). These experiments demonstrated that benthic bacteria dominated the consumption of phytodetritus over short (~ 1.5 d) time scales, with metazoan macrofauna playing a minor role. These results contrast with the only other comparable in situ abyssal study, where macrofauna dominated phytodetritus assimilation over short (2.5 d) time scales in the eutrophic NE Atlantic. We also demonstrated that benthic bacteria were capable of converting dissolved inorganic C into biomass and showed that this process can occur at rates that are as high as the bacterial assimilation of algal-derived organic C. This demonstrates the potential importance of inorganic C uptake to abyssal ecosystems in this region. It also alludes to the possibility that some of the C incorporation by bacteria in our algal-addition studies may have resulted from the incorporation of labeled dissolved inorganic carbon initially respired by other unstudied organisms. Our findings reveal the key importance of benthic bacteria in the short-term cycling of C in abyssal habitats in the eastern CCFZ and provide important information on benthic ecosystem functioning in an area targeted for commercial-scale, deep-sea mining activities.

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e-pub ahead of print date: 16 November 2018
Published date: 1 March 2019

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Local EPrints ID: 429601
URI: http://eprints.soton.ac.uk/id/eprint/429601
ISSN: 0024-3590
PURE UUID: bd6398af-c4b9-45db-a11e-fa3fa45eb3ef

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Date deposited: 01 Apr 2019 16:30
Last modified: 07 Oct 2020 00:15

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Contributors

Author: Andrew K. Sweetman
Author: Craig R. Smith
Author: Christine N. Shulse
Author: Brianne Maillot
Author: Markus Lindh
Author: Matthew J. Church
Author: Kirstin S. Meyer
Author: Dick van Oevelen
Author: Tanja Stratmann
Author: Andrew J. Gooday

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