The potential role of Antarctic krill faecal pellets in efficient carbon export at the marginal ice zone of the South Orkney Islands in spring
The potential role of Antarctic krill faecal pellets in efficient carbon export at the marginal ice zone of the South Orkney Islands in spring
Antarctic krill (Euphausia superba) play a central role in the food web of the Southern Ocean, forming a link between primary production and large predators. Krill produce large, faecal pellets (FP) which can form a large component of mesopelagic particulate organic carbon (POC) fluxes. However, the patchy distribution of krill swarms, highly variable pellet composition, and variable sinking and attenuation rates means that these episodic, but potentially large, carbon fluxes are difficult to sample or model. We measured particle flux and type using Marine Snow Catchers (MSC) in the marginal ice zone near the South Orkneys, Antarctica. Krill FP were the dominant component of the POC flux in the upper 200 m (typically 60-85%). FP sinking velocities measured onboard were highly variable (15-507 m d-1) but overall high, with mean equivalent velocities of 172, 267 and 161 m d-1 at our three stations. The high numbers of krill FP sinking through the mesopelagic suggest that krill FP can be transferred efficiently and/or that rates of krill FP production are high. We compared our direct MSC-derived estimates of krill FP POC flux (33-154 mg C m-2 d-1) and attenuation to estimates of krill FP production based on previous measurements of krill density and literature FP egestion rates, and estimated net krill FP attenuation rates in the upper mesopelagic. Calculated attenuation rates are sensitive to krill densities in the overlying water column but suggest that krill FP could be transferred efficiently through the upper mesopelagic, and, in agreement with our MSC attenuation estimates, could make large contributions to bathypelagic POC fluxes. Our study contrasts with some others which suggest rapid FP attenuation, highlighting the need for further work to constrain attenuation rates and assess how important the contribution of Antarctic krill FP could be to the Southern Ocean biological carbon pump.
2001-2013
Belcher, A.
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Tarling, G.A.
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Manno, C.
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Atkinson, A.
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Ward, P.
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Skaret, G.
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Fielding, S.
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Henson, S.A.
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Sanders, R.
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1 October 2017
Belcher, A.
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Tarling, G.A.
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Manno, C.
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Atkinson, A.
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Ward, P.
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Skaret, G.
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Fielding, S.
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Henson, S.A.
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Sanders, R.
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Belcher, A., Tarling, G.A., Manno, C., Atkinson, A., Ward, P., Skaret, G., Fielding, S., Henson, S.A. and Sanders, R.
(2017)
The potential role of Antarctic krill faecal pellets in efficient carbon export at the marginal ice zone of the South Orkney Islands in spring.
Polar Biology, 40 (10), .
(doi:10.1007/s00300-017-2118-z).
Abstract
Antarctic krill (Euphausia superba) play a central role in the food web of the Southern Ocean, forming a link between primary production and large predators. Krill produce large, faecal pellets (FP) which can form a large component of mesopelagic particulate organic carbon (POC) fluxes. However, the patchy distribution of krill swarms, highly variable pellet composition, and variable sinking and attenuation rates means that these episodic, but potentially large, carbon fluxes are difficult to sample or model. We measured particle flux and type using Marine Snow Catchers (MSC) in the marginal ice zone near the South Orkneys, Antarctica. Krill FP were the dominant component of the POC flux in the upper 200 m (typically 60-85%). FP sinking velocities measured onboard were highly variable (15-507 m d-1) but overall high, with mean equivalent velocities of 172, 267 and 161 m d-1 at our three stations. The high numbers of krill FP sinking through the mesopelagic suggest that krill FP can be transferred efficiently and/or that rates of krill FP production are high. We compared our direct MSC-derived estimates of krill FP POC flux (33-154 mg C m-2 d-1) and attenuation to estimates of krill FP production based on previous measurements of krill density and literature FP egestion rates, and estimated net krill FP attenuation rates in the upper mesopelagic. Calculated attenuation rates are sensitive to krill densities in the overlying water column but suggest that krill FP could be transferred efficiently through the upper mesopelagic, and, in agreement with our MSC attenuation estimates, could make large contributions to bathypelagic POC fluxes. Our study contrasts with some others which suggest rapid FP attenuation, highlighting the need for further work to constrain attenuation rates and assess how important the contribution of Antarctic krill FP could be to the Southern Ocean biological carbon pump.
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Accepted/In Press date: 26 March 2017
e-pub ahead of print date: 13 April 2017
Published date: 1 October 2017
Organisations:
Ocean and Earth Science, Ocean Biochemistry & Ecosystems, Marine Biogeochemistry, National Oceanography Centre
Identifiers
Local EPrints ID: 406905
URI: http://eprints.soton.ac.uk/id/eprint/406905
ISSN: 0722-4060
PURE UUID: 94e60a04-a307-4257-88c8-0c1ff41767e3
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Date deposited: 28 Mar 2017 01:02
Last modified: 15 Mar 2024 12:58
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Contributors
Author:
A. Belcher
Author:
G.A. Tarling
Author:
C. Manno
Author:
A. Atkinson
Author:
P. Ward
Author:
G. Skaret
Author:
S. Fielding
Author:
R. Sanders
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