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Seasonal variations, origin, and fate of settling diatoms in the Southern Ocean tracked by silicon isotope records in deep sediment traps


Closset, I and Cardinal, D and Bray, SG and Thil, F and Djouraev, I and Rigual-Hernandez, AS and Trull, TW, Seasonal variations, origin, and fate of settling diatoms in the Southern Ocean tracked by silicon isotope records in deep sediment traps, Global Biogeochemical Cycles, 29, (9) pp. 1495-1510. ISSN 0886-6236 (2015) [Refereed Article]


Copyright Statement

2015. American Geophysical Union. All Rights Reserved.

DOI: doi:10.1002/2015GB005180


The Southern Ocean plays a pivotal role in the control of atmospheric CO2 levels, via both physical and biological sequestration processes. The biological carbon transfer to the ocean interior is tightly coupled to the availability of other elements, especially iron as a trace-limiting nutrient and dissolved silicon as the mineral substrate that allows diatoms to dominate primary production. Importantly, variations in the silicon cycling are large but not well understood. Here we use δ30Si measurements to track seasonal flows of silica to the deep sea, as captured by sediment trap time series, for the three major zones (Antarctic, AZ; Polar Frontal, PFZ; and Sub-Antarctic, SAZ) of the open Southern Ocean. Variations in the exported flux of biogenic silica (BSi) and its δ30Si composition reveal a range of insights, including that (i) the sinking rate of BSi exceeds 200 m d−1 in summer in the AZ yet decreases to very low values in winter that allow particles to remain in the water column through to the following spring, (ii) occasional vertical mixing events affect the δ30Si composition of exported BSi in both the SAZ and AZ, and (iii) the δ30Si signature of diatoms is well conserved through the water column despite strong BSi and particulate organic carbon (POC) attenuation at depth and is closely linked to the Si consumption in surface waters. With the strong coupling observed between BSi and POC fluxes in PFZ and AZ, these data provide new constraints for application to biogeochemical models of seasonal controls on production and export.

Item Details

Item Type:Refereed Article
Keywords:silicon isotope, sediment traps, Southern Ocean, particle settling rates, biogeochemical models
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Bray, SG (Mr Stephen Bray)
UTAS Author:Trull, TW (Professor Thomas Trull)
ID Code:106060
Year Published:2015
Web of Science® Times Cited:23
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2016-01-27
Last Modified:2017-10-31
Downloads:221 View Download Statistics

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