Late quaternary variations of elemental ratios (C/Si and N/Si) in diatom-bound organic matter from the Southern Ocean

Xavier Crosta*, Aldo Shemesh, Marie Eve Salvignac, Hezi Gildor, Ruth Yam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The carbon cycle in the Southern Ocean is considered as a major factor controlling past atmospheric CO2 concentration variations. However, accumulation rates of biogenic opal are not linearly related to carbon burial rates. Here, we show that it is possible to measure the carbon and nitrogen content of diatom-bound organic matter (%Cdiat and %Ndiat, respectively) and that the signals recorded do not appear to be analytical artifacts. Analyses of two cores from the Atlantic and Indian sectors of the Southern Ocean show that %Cdiat and %Ndiat change on glacial-interglacial cycles by 30-40% and 120-175%, respectively. Accordingly, C/N ratios vary between 3 and 7 on glacial-interglacial timescales. If changes recorded in the occluded organic matter are representative of the changes in the diatom bulk organic matter, this provides a new tool to document the carbon cycle in the Southern Ocean and to determine its role on past atmospheric pCO2 variations. Laboratory experiments on diatom cultures are needed to validate the use of diatom organic bound C and N as a tracer of diatom physiology and of carbon export from surface waters.

Original languageAmerican English
Pages (from-to)1939-1952
Number of pages14
JournalDeep-Sea Research Part II: Topical Studies in Oceanography
Issue number9-10
StatePublished - 2002
Externally publishedYes

Bibliographical note

Funding Information:
We thank David Hodell and D. Paillard for constructive discussions, Lloyd Burckle and two other reviewers for helpful comments that improved the manuscript. We also thank people from SO136 TASQWA cruise, especially Elisa Laurent for recovering the samples. Oxygen isotope analyses were performed in Gif sur Yvette, France. Financial support for this research was provided by European TMR Program, Feinberg Fellowship Program (BSF Israel-US Binational Science Foundation), CNRS (Centre National de la Recherche Scientifique), PNEDC (Programme National d’Etude de la Dynamique du Climat), and Missions Scientifiques des Terres Australes et Antarctiques Françaises (IFRTP-TAAF). This is DGO contribution No. 1398.


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