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Relevance of silicon isotopes to Si-nutrient utilization and Si-source assessment in Antarctic waters


Cardinal, D and Alleman, LY and Dehairs, F and Savoye, N and Trull, T and Andre, L, Relevance of silicon isotopes to Si-nutrient utilization and Si-source assessment in Antarctic waters, Global Biogeochemical Cycles, 19, (2) pp. GB2007. ISSN 0886-6236 (2005) [Refereed Article]

DOI: doi:10.1029/2004GB002364


We analyzed δ29Si of dissolved silicate for eight water column profiles across the Southern Ocean (south of Australia in spring 2001) from the Seasonal Ice Zone (SIZ) north to the Subantarctic Zone (SAZ), including the first isotopic compositions measured for Si-depleted seawaters. All profiles display mixed layer enrichments in heavy Si isotopes relative to deep water in accordance with preferential uptake of the light isotope by diatoms. As silicate levels decrease from the SIZ northward across the Polar Front Zone (PFZ) to the SAZ, surface and mesopelagic δ29Si signatures generally become progressively heavier, but the most Si-depleted SAZ waters do not exhibit δ29Si values heavier than in the PFZ. This intricacy appears to derive from variations in the vertical and horizontal supply of silicate to surface waters, and by applying a steady state open system model, we estimate a fractionation factor, 29ε, between diatoms and seawater of -0.45 ± 0.17‰, independently of zones and phytoplankton community. Though encouraging, these results are related to latitudinal changes in mesopelagic δ29Si values, complexity in surface silicate-δ29Si correlations, and differences from previous studies, which underline the need for caution in the use of silicon isotopes in paleoceanographic studies until systematic efforts have been undertaken to better understand modern variations. Copyright 2005 by the American Geophysical Union.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical oceanography
Objective Division:Environmental Management
Objective Group:Marine systems and management
Objective Field:Oceanic processes (excl. in the Antarctic and Southern Ocean)
UTAS Author:Trull, T (Professor Thomas Trull)
ID Code:38794
Year Published:2005
Web of Science® Times Cited:114
Deposited By:CRC-Antarctic Climate & Ecosystems
Deposited On:2005-08-01
Last Modified:2011-07-18

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