Potential role of giant marine diatoms in sequestration of atmospheric CO2 during the Last Glacial Maximum: δ13C evidence from laminated Ethmodiscus rex mats in tropical West Pacific - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Global and Planetary Change Année : 2013

Potential role of giant marine diatoms in sequestration of atmospheric CO2 during the Last Glacial Maximum: δ13C evidence from laminated Ethmodiscus rex mats in tropical West Pacific

Résumé

Giant marine diatoms, blooming or aggregating within deep chlorophyll maxima under stratified conditions, can generate substantial production and a large export flux of organic carbon from surface waters. However, their role in regulating glacial-interglacial variation in atmospheric pCO 2 remains unclear. Here, we report the organic carbon isotopic compositions of Ethmodiscus rex diatoms (δ 13 C E. rex) and bulk sediments (δ 13 C org) from a sediment core in the eastern Philippine Sea dated to ~19.5-31.0 kyr B.P. and consisting of (from youngest to oldest) (1) laminated E. rex diatom mats (LDM), (2) diatomaceous clay (DC), and (3) pelagic clay (PC). Our results suggest that δ 13 C E. rex provides a better record of palaeoceanographic processes during LDM and DC deposition than δ 13 C org because of reduced differential vital effects in near-monospecific E. rex fractions. We used the isotopic composition of the coarse E. rex fraction (δ 13 C E. rex (>154 μm)) to calculate the CO 2 partial pressure of eastern Philippine Sea surface waters (pCO 2-sw) during the Last Glacial Maximum (LGM). Our pCO 2-sw records suggest that the eastern Philippine Sea switched from being a strong CO 2 source during DC deposition to a weak CO 2 sink during LDM deposition. The role of the eastern Philippine Sea as a CO 2 sink during the LGM was promoted by elevated primary production and, to a lesser extent, intensified water-column stratification. These observations highlight the potential role of giant marine diatoms in the sequestration of atmospheric CO 2 during the LGM and, hence, support changes in biogenic silica fluxes as a potential cause of lower glacial atmospheric CO 2. Our findings are consistent with an eolian source of silica, as proposed by the 'silica hypothesis' and the 'silicon-induced alkalinity pump hypothesis' but not by the 'silicic acid leakage hypothesis.'
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hal-02105590 , version 1 (21-04-2019)

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Zhifang Xiong, Tiegang Li, Xavier Crosta, Thomas Algeo, Fengming Chang, et al.. Potential role of giant marine diatoms in sequestration of atmospheric CO2 during the Last Glacial Maximum: δ13C evidence from laminated Ethmodiscus rex mats in tropical West Pacific. Global and Planetary Change, 2013, 108, pp.1-14. ⟨10.1016/j.gloplacha.2013.06.003⟩. ⟨hal-02105590⟩

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