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

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

Research output: Contribution to journalArticle

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 have been undertaken in situ. We undertook 8 in situ pulse-chase experiments in 3 abyssal strata (4050-4200 m water depth) separated by 10s to 100s of kilometres in the eastern Clarion-Clipperton Fracture Zone. 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 DIC 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.
LanguageEnglish
JournalLimnology and Oceanography
Publication statusAccepted/In press - 5 Oct 2018

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seafloor
phytodetritus
bacterium
carbon
ocean
timescale
experiment
metazoan
ecosystem function
fracture zone
deep sea
water depth
ecosystem
biomass
habitat
sediment
in situ
assimilation
organism
incorporation

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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 ; Gooday, Andrew J. / Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low POC flux region of the eastern Pacific Ocean. In: Limnology and Oceanography. 2018.
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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 have been undertaken in situ. We undertook 8 in situ pulse-chase experiments in 3 abyssal strata (4050-4200 m water depth) separated by 10s to 100s of kilometres in the eastern Clarion-Clipperton Fracture Zone. 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 DIC 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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Sweetman, AK, Smith, CR, Shulse, CN, Maillot, B, Lindh, M, Church, MJ, Meyer, KS, van Oevelen, D, Stratmann, T & Gooday, AJ 2018, 'Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low POC flux region of the eastern Pacific Ocean', Limnology and Oceanography.

Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low POC flux region of the eastern Pacific Ocean. / Sweetman, Andrew K.; Smith, Craig R.; Shulse, Christine N.; Maillot, Brianne; Lindh, Markus; Church, Matthew J.; Meyer, Kirstin S.; van Oevelen, Dick; Stratmann, Tanja; Gooday, Andrew J.

In: Limnology and Oceanography, 05.10.2018.

Research output: Contribution to journalArticle

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T1 - Key role of bacteria in the short-term cycling of carbon at the abyssal seafloor in a low POC flux region of the eastern Pacific Ocean

AU - Sweetman, Andrew K.

AU - Smith, Craig R.

AU - Shulse, Christine N.

AU - Maillot, Brianne

AU - Lindh, Markus

AU - Church, Matthew J.

AU - Meyer, Kirstin S.

AU - van Oevelen, Dick

AU - Stratmann, Tanja

AU - Gooday, Andrew J.

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N2 - 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 have been undertaken in situ. We undertook 8 in situ pulse-chase experiments in 3 abyssal strata (4050-4200 m water depth) separated by 10s to 100s of kilometres in the eastern Clarion-Clipperton Fracture Zone. 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 DIC 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.

AB - 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 have been undertaken in situ. We undertook 8 in situ pulse-chase experiments in 3 abyssal strata (4050-4200 m water depth) separated by 10s to 100s of kilometres in the eastern Clarion-Clipperton Fracture Zone. 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 DIC 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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