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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
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.
0722-4060
2001-2013
Belcher, A.
604905f0-adc0-4503-b8b3-d5b5f9960771
Tarling, G.A.
11c6c41e-2840-4c60-b262-b404e58607ee
Manno, C.
c49cdab0-866e-44fe-b504-e3c9a9924d86
Atkinson, A.
c2fcdbc8-0f24-4529-8926-2546d00c9c9a
Ward, P.
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Skaret, G.
99d099c8-e332-4160-bc0c-aa59c34a6b27
Fielding, S.
b6810aca-528b-41d9-b23e-3e05647c5fab
Henson, S.A.
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Sanders, R.
02c163c1-8f5e-49ad-857c-d28f7da66c65
Belcher, A.
604905f0-adc0-4503-b8b3-d5b5f9960771
Tarling, G.A.
11c6c41e-2840-4c60-b262-b404e58607ee
Manno, C.
c49cdab0-866e-44fe-b504-e3c9a9924d86
Atkinson, A.
c2fcdbc8-0f24-4529-8926-2546d00c9c9a
Ward, P.
3b08352b-fe2b-40a0-8dd3-b4e34b5c30cd
Skaret, G.
99d099c8-e332-4160-bc0c-aa59c34a6b27
Fielding, S.
b6810aca-528b-41d9-b23e-3e05647c5fab
Henson, S.A.
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Sanders, R.
02c163c1-8f5e-49ad-857c-d28f7da66c65

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), 2001-2013. (doi:10.1007/s00300-017-2118-z).

Record type: Article

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: https://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: 09 Dec 2019 18:56

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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: S.A. Henson
Author: R. Sanders

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