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The role of particle associated microbes in remineralisation of faecal pellets in the upper mesopelagic of the Scotia Sea, Antarctica

The role of particle associated microbes in remineralisation of faecal pellets in the upper mesopelagic of the Scotia Sea, Antarctica
The role of particle associated microbes in remineralisation of faecal pellets in the upper mesopelagic of the Scotia Sea, Antarctica
Fecal pellets (FP) are a key component of the biological carbon pump, as they can, under some circumstances, efficiently transfer carbon to depth. Like other forms of particulate organic carbon (POC), they can be remineralized in the ocean interior (particularly in the upper 200 m), or alternatively they can be preserved in the sediments. The controls on the attenuation of FP flux with depth are not fully understood, in particular, the relative contributions of zooplankton fragmentation and microbial/zooplankton respiration to FP loss. Collection of sinking particles using Marine Snow Catchers at three ecologically contrasting sites in the Scotia Sea, Antarctica, revealed large differences in POC flux composition (5–96% FP) and flux attenuation despite similar temperatures. To determine the importance of microbial respiration on FP loss in the upper mesopelagic, we made the first ever measurements of small scale oxygen gradients through the boundary layer at the interface of krill FP collected from the Scotia Sea. Estimated carbon-specific respiration rates of microbes within FP (0.010–0.065 d?1) were too low to account for the observed large decreases in FP flux over the upper 200 m. Therefore, the observed rapid declines in downward FP flux in the upper mesopelagic are more likely to be caused by zooplankton, through coprophagy, coprorhexy, and coprochaly. Microbial respiration is likely to be more important in regions of higher temperatures, and at times of the year, or in depths of the ocean, where zooplankton abundances are low and therefore grazing and fragmentation processes are reduced.
0024-3590
1049-1064
Belcher, Anna
604905f0-adc0-4503-b8b3-d5b5f9960771
Iversen, Morten
2a6ac285-5121-4cb9-93a7-4ead156a1427
Manno, Clara
c49cdab0-866e-44fe-b504-e3c9a9924d86
Henson, Stephanie A.
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Tarling, Geraint A.
d7d95281-b939-4f83-8e5c-224949844dcc
Sanders, Richard
02c163c1-8f5e-49ad-857c-d28f7da66c65
Belcher, Anna
604905f0-adc0-4503-b8b3-d5b5f9960771
Iversen, Morten
2a6ac285-5121-4cb9-93a7-4ead156a1427
Manno, Clara
c49cdab0-866e-44fe-b504-e3c9a9924d86
Henson, Stephanie A.
d6532e17-a65b-4d7b-9ee3-755ecb565c19
Tarling, Geraint A.
d7d95281-b939-4f83-8e5c-224949844dcc
Sanders, Richard
02c163c1-8f5e-49ad-857c-d28f7da66c65

Belcher, Anna, Iversen, Morten, Manno, Clara, Henson, Stephanie A., Tarling, Geraint A. and Sanders, Richard (2016) The role of particle associated microbes in remineralisation of faecal pellets in the upper mesopelagic of the Scotia Sea, Antarctica. Limnology and Oceanography, 61 (3), 1049-1064. (doi:10.1002/lno.10269).

Record type: Article

Abstract

Fecal pellets (FP) are a key component of the biological carbon pump, as they can, under some circumstances, efficiently transfer carbon to depth. Like other forms of particulate organic carbon (POC), they can be remineralized in the ocean interior (particularly in the upper 200 m), or alternatively they can be preserved in the sediments. The controls on the attenuation of FP flux with depth are not fully understood, in particular, the relative contributions of zooplankton fragmentation and microbial/zooplankton respiration to FP loss. Collection of sinking particles using Marine Snow Catchers at three ecologically contrasting sites in the Scotia Sea, Antarctica, revealed large differences in POC flux composition (5–96% FP) and flux attenuation despite similar temperatures. To determine the importance of microbial respiration on FP loss in the upper mesopelagic, we made the first ever measurements of small scale oxygen gradients through the boundary layer at the interface of krill FP collected from the Scotia Sea. Estimated carbon-specific respiration rates of microbes within FP (0.010–0.065 d?1) were too low to account for the observed large decreases in FP flux over the upper 200 m. Therefore, the observed rapid declines in downward FP flux in the upper mesopelagic are more likely to be caused by zooplankton, through coprophagy, coprorhexy, and coprochaly. Microbial respiration is likely to be more important in regions of higher temperatures, and at times of the year, or in depths of the ocean, where zooplankton abundances are low and therefore grazing and fragmentation processes are reduced.

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Accepted/In Press date: January 2016
e-pub ahead of print date: 11 February 2016
Published date: May 2016
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 385797
URI: https://eprints.soton.ac.uk/id/eprint/385797
ISSN: 0024-3590
PURE UUID: de6aeea2-2f8e-4517-a6cf-c9e12c47a7fe

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Date deposited: 12 Jan 2016 10:11
Last modified: 14 Aug 2019 18:29

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