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Settling fluxes of diatoms to the interior of the antarctic circumpolar current along 170°W

Settling fluxes of diatoms to the interior of the antarctic circumpolar current along 170°W
Settling fluxes of diatoms to the interior of the antarctic circumpolar current along 170°W
An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170°W, between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antarctic Polar Front, the Antarctic Zone and the Southern Antarctic Zone. Here we report observations from 1000 m below the sea-surface compared to seafloor and surface water distributions. Sub-sample splits from each trap were obtained and total diatom flux and species composition were determined. The diatom fluxes were quantified using both a dilution and a ‘spike’ method to allow for the rapid repeatability of measurements. Diatom flux was found to be highly seasonal across the ACC particularly at higher latitudes. Marine snow aggregates of intact diatom cells and chains were the major component of the biogenic flux. Siliceous particle size was noted to decrease with increasing latitude, which could be aligned with a shift of the diatom assemblage to small-size species/sea-ice affiliated species. A “double-structured” diatom flux was recorded at the location of the Antarctic Polar Front trap, with a shift in the diatom assemblage from larger to smaller diatoms in the second flux episode. The sediment trap assemblage shows deviations from the surface water assemblage, while surface sediment samples indicate that significant dissolution occurs after 1000 m and at the sediment-water interface. Estimation of diatom biovolumes across the ACC shows that large diatoms have the potential to greatly impact biogenic fluxes to the ocean interior despite their low fluxes. Small species of the genus Fragilariopsis could potentially export as much Corg as F. kerguelensis near the retreating ice edge. However, their low abundance in the surface sediments also suggests that these diatoms are a shallow export species.
Diatom flux, Particulate flux, Sediment traps, Marine snow, Ross sea, Southwest Pacific
0967-0637
1-13
Grigorov, Ivo
029a4051-ae71-48bd-a55f-01e6c27a91da
Rigual-Hernandez, Andrés S.
d7cffd42-21cf-41fb-b2ed-1a9cd00862e0
Honjo, Susumu
ce46d714-1358-47d2-9316-aa96b0c183f7
Kemp, Alan E.S.
131b479e-c2c4-47ae-abe1-ad968490960e
Armand, Leanne K.
01b06f02-4404-4c8b-bcb9-39d542edc4a1
Grigorov, Ivo
029a4051-ae71-48bd-a55f-01e6c27a91da
Rigual-Hernandez, Andrés S.
d7cffd42-21cf-41fb-b2ed-1a9cd00862e0
Honjo, Susumu
ce46d714-1358-47d2-9316-aa96b0c183f7
Kemp, Alan E.S.
131b479e-c2c4-47ae-abe1-ad968490960e
Armand, Leanne K.
01b06f02-4404-4c8b-bcb9-39d542edc4a1

Grigorov, Ivo, Rigual-Hernandez, Andrés S., Honjo, Susumu, Kemp, Alan E.S. and Armand, Leanne K. (2014) Settling fluxes of diatoms to the interior of the antarctic circumpolar current along 170°W. Deep Sea Research Part I: Oceanographic Research Papers, 93, 1-13. (doi:10.1016/j.dsr.2014.07.008).

Record type: Article

Abstract

An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170°W, between November 1996 and January 1998, as part of the US JGOFS-Antarctic Environment and Southern Ocean Process Study (AESOPS) program. The trap locations represent sampling within the Polar Frontal Zone, the Antarctic Polar Front, the Antarctic Zone and the Southern Antarctic Zone. Here we report observations from 1000 m below the sea-surface compared to seafloor and surface water distributions. Sub-sample splits from each trap were obtained and total diatom flux and species composition were determined. The diatom fluxes were quantified using both a dilution and a ‘spike’ method to allow for the rapid repeatability of measurements. Diatom flux was found to be highly seasonal across the ACC particularly at higher latitudes. Marine snow aggregates of intact diatom cells and chains were the major component of the biogenic flux. Siliceous particle size was noted to decrease with increasing latitude, which could be aligned with a shift of the diatom assemblage to small-size species/sea-ice affiliated species. A “double-structured” diatom flux was recorded at the location of the Antarctic Polar Front trap, with a shift in the diatom assemblage from larger to smaller diatoms in the second flux episode. The sediment trap assemblage shows deviations from the surface water assemblage, while surface sediment samples indicate that significant dissolution occurs after 1000 m and at the sediment-water interface. Estimation of diatom biovolumes across the ACC shows that large diatoms have the potential to greatly impact biogenic fluxes to the ocean interior despite their low fluxes. Small species of the genus Fragilariopsis could potentially export as much Corg as F. kerguelensis near the retreating ice edge. However, their low abundance in the surface sediments also suggests that these diatoms are a shallow export species.

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More information

Accepted/In Press date: July 2014
e-pub ahead of print date: 25 July 2014
Published date: November 2014
Keywords: Diatom flux, Particulate flux, Sediment traps, Marine snow, Ross sea, Southwest Pacific
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 367416
URI: http://eprints.soton.ac.uk/id/eprint/367416
ISSN: 0967-0637
PURE UUID: 9a02fcc7-fd36-45e6-af17-358aa6538b2a

Catalogue record

Date deposited: 29 Jul 2014 15:15
Last modified: 14 Mar 2024 17:29

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Contributors

Author: Ivo Grigorov
Author: Andrés S. Rigual-Hernandez
Author: Susumu Honjo
Author: Alan E.S. Kemp
Author: Leanne K. Armand

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