Settling fluxes of diatoms to the interior of the Antarctic circumpolar current along 170 1W

Ivo Grigorov, A.S. Rigual-Hernandez, Susumu Honjo, A.E.S. Kemp

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

An array of four sediment trap moorings recorded the particulate flux across the Antarctic Circumpolar Current (ACC) at 170 1 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 sea floor 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 components 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 af filiated 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 C org as Fragilariopsis kerguelensis near the retreating ice edge. However, their low abundance in the surface sediments also suggests that these diatoms are a shallow export species
Original languageEnglish
JournalDeep-Sea Research Part I: Oceanographic Research Papers
Volume93
Pages (from-to)1-13
ISSN0967-0637
DOIs
Publication statusPublished - 2014
Externally publishedYes

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