Carbon Isotopic Fractionation of Alkenones and Gephyrocapsa Coccoliths Over the Late Quaternary (Marine Isotope Stages 12–9) Glacial-Interglacial Cycles at the Western Tropical Atlantic

A. González-Lanchas; I. Hernández-Alméida; J.-A. FloresF. J. SierroJ. GuitianH. M. Stoll

首页> 外文期刊>Paleoceanography >Carbon Isotopic Fractionation of Alkenones and Gephyrocapsa Coccoliths Over the Late Quaternary (Marine Isotope Stages 12–9) Glacial-Interglacial Cycles at the Western Tropical Atlantic

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Carbon Isotopic Fractionation of Alkenones and Gephyrocapsa Coccoliths Over the Late Quaternary (Marine Isotope Stages 12–9) Glacial-Interglacial Cycles at the Western Tropical Atlantic

机译：Carbon Isotopic Fractionation of Alkenones and Gephyrocapsa Coccoliths Over the Late Quaternary (Marine Isotope Stages 12–9) Glacial-Interglacial Cycles at the Western Tropical Atlantic

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The sensitivity of coccolithophores to changing CO_2 and its role modulating cellular photosynthetic carbon isotopic fractionation (ε_p) is crucial to understand the future adaptation of these organisms to higher CO_2 world and to assess the reliability of εp for past CO_2 estimation. Here, we present ε_p measured on natural fossil samples across the glacial-interglacial (G-I) CO_2 variations of marine isotope stages 12 to 9 interval (454–334 ka) at the western tropical Atlantic Ocean Drilling Program Site 925 together with a set of organic and inorganic geochemical, micropaleontological and morphometrical data from Gephyrocapsa coccoliths in the same samples. The ~2‰ variation in ε_p is significantly correlated with the CO_2[aq] concentrations calculated from assumption of air-sea equilibrium with measured ice core pCO_2 concentrations. The sensitivity of ε_p to CO_2[aq] is similar to that derived from a multiple regression model of culture observations and is not well simulated with the classical purely diffusive model of algal CO_2 acquisition. The measured range of Gephyrocapsa cell sizes is insufficient to explain the non-CO_2 effects on ε_p at this location, via either direct size effect or growth rate correlated to cell size. Primary productivity, potentially triggered by shifting growth rates and light levels, may also affect ε_p. Proposed productivity proxies % Florisphaera profunda and the ratio between the C_(37) to C_(38.et) alkenone (C37/C38.et ratio) both correlates modestly with the non-CO_2 effects on ε_p. When the observed G-I ε_p to CO_2 sensitivity at this site is used to estimate pCO_2 from ε_p since the Miocene, the inferred pCO_2 declines are larger in amplitude compared to that calculated from a theoretical ε_p diffusive model. We find that oxygen and carbon stable isotope vital effects in the near monogeneric-separated Gephyrocapsa coccoliths (respectively Δδ~(18)O_(Gephyrocapsa–Trilobatus sacculifer) and ε_(coccolith)) are c

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来源
《Paleoceanography》 |2021年第8期|e2020PA004175-1-e2020PA004175-28|共28页
作者
A. González-Lanchas; I. Hernández-Alméida; J.-A. FloresF. J. SierroJ. GuitianH. M. Stoll;
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作者单位

Departamento de Geología, Universidad de Salamanca, Salamanca, Spain;

Geological Institute, ETH Zu?rich, Zu?rich, Switzerland;

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正文语种英语
中图分类海洋学;
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Carbon Isotopic Fractionation; Alkenones and Gephyrocapsa; Glacial-Interglacial Cycles;

Carbon Isotopic Fractionation of Alkenones and Gephyrocapsa Coccoliths Over the Late Quaternary (Marine Isotope Stages 12–9) Glacial-Interglacial Cycles at the Western Tropical Atlantic

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