The silicon isotope composition of Ethmodiscus rex laminated diatom mats from the tropical West Pacific: Implications for silicate cycling during the Last Glacial Maximum - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Paleoceanography Année : 2015

The silicon isotope composition of Ethmodiscus rex laminated diatom mats from the tropical West Pacific: Implications for silicate cycling during the Last Glacial Maximum

Zhifang Xiong
  • Fonction : Auteur
Tiegang Li
  • Fonction : Auteur
Kristin Doering
  • Fonction : Auteur
Fengming Chang
  • Fonction : Auteur
Sophie Opfergelt
  • Fonction : Auteur
  • PersonId : 860494
Xavier Crosta
Fuqing Jiang
  • Fonction : Auteur
Shiming Wan
  • Fonction : Auteur
Bin Zhai
  • Fonction : Auteur

Résumé

The cause of massive blooms of Ethmodiscus rex laminated diatom mats (LDMs) in the eastern Philippine Sea (EPS) during the Last Glacial Maximum (LGM) remains uncertain. In order to better understand the mechanism of formation of E. rex LDMs from the perspective of dissolved silicon (DSi) utilization, we determined the silicon isotopic composition of single E. rex diatom frustules (δ 30 Si E. rex) from two sediment cores in the Parece Vela Basin of the EPS. In the study cores, δ 30 Si E. rex varies from À1.23‰ to À0.83‰ (average À1.04‰), a range that is atypical of marine diatom δ 30 Si and that corresponds to the lower limit of reported diatom δ 30 Si values of any age. A binary mixing model (upwelled silicon versus eolian silicon) accounting for silicon isotopic fractionation during DSi uptake by diatoms was constructed. The binary mixing model demonstrates that E. rex dominantly utilized DSi from eolian sources (i.e., Asian dust) with only minor contributions from upwelled seawater sources (i.e., advected from Subantarctic Mode Water, Antarctic Intermediate Water, or North Pacific Intermediate Water). E. rex utilized only ~24% of available DSi, indicating that surface waters of the EPS were eutrophic with respect to silicon during the LGM. Our results suggest that giant diatoms did not always use a buoyancy strategy to obtain nutrients from the deep nutrient pool, thus revising previously proposed models for the formation of E. rex LDMs.
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Dates et versions

hal-02105557 , version 1 (21-04-2019)

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Zhifang Xiong, Tiegang Li, Thomas Algeo, Kristin Doering, Martin Frank, et al.. The silicon isotope composition of Ethmodiscus rex laminated diatom mats from the tropical West Pacific: Implications for silicate cycling during the Last Glacial Maximum. Paleoceanography, 2015, 30 (7), pp.803-823. ⟨10.1002/2015PA002793⟩. ⟨hal-02105557⟩

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