EGU2020-19994
https://doi.org/10.5194/egusphere-egu2020-19994
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

δ11B and B/Ca ontogenetic variability within Globigerina bulloides

Matthieu Buisson1, Pascale Louvat1, Szabina Karancz2,3, Ruchen Tian2,4, Markus Raitzsch2,5, Jelle Bijma2,6, and Claire Rollion-Bard1
Matthieu Buisson et al.
  • 1Institut de Physique du Globe de Paris, CNRS, University of Paris , Paris, France (mbuisson@ipgp.fr)
  • 2Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 3Royal Netherlands Institute for Sea Research, Utrecht University, Texel, The Netherlands
  • 4Eberhard Karls Universität Tübingen, Tübingen, Germany
  • 5MARUM - Centre for Marine Environmental Sciences, University of Bremen, Bremen, Germany
  • 6Jacobs University, Bremen, Germany

Understanding the atmosphere-continent-ocean carbon cycle and its associated oceanic carbon system is one of the keystones to face the Anthropocene’s climate change. Since the 1990s the isotopic ratio of boron (δ11B) in calcitic shells of planktonic foraminifera has proven to be a powerful geochemical proxy to determine the oceanic paleo-pH and its link to atmospheric CO2 level over geological times1, whereas the ratio B/Ca as proxy of the seawater carbonate chemistry is still questionable2,3.

However, the use of planktonic foraminifera in paleoclimatic reconstructions requires calibrations of the pH – δ11B relationships to correct what is known as « vital effect »4: each species controls differently its calcification process and consequently slightly modifies the seawater chemistry during biomineralization5,6. Moreover, shell size effect on δ11B has been reported for some symbiont-bearing species due to photosynthetic increase of pH7,8.

Calibrations for the symbiont-barren Globigerina bulloides have been already determined9,10 but sparse data have been reported so far for the test size effect on δ11B 11.

Here we measured the δ11B of three different fractions (250-315, 315-400 and >400 μm) of G. bulloides sampled along the coretop PS97-122 from the Chilean margin (54.10°S, 74.91°W), by using a new protocol developed at IPGP and dedicated to small samples which couple a microsublimation technique and a micro-direct injection device (μ-dDIHEN12). Our preliminary results show significantly higher δ11B values for the large fractions compared to the small ones, as found for symbiont-bearing planktonic species such as Globigerinoides sacculifer7 and Globigerinoides ruber8.

 

  • (1) Pearson & Palmer, 2000, Nature 406, 695-699
  • (2) Yu et al., 2007, Paleoceanography 22, PA2202
  • (3) Allen et al., 2012, EPSL 351-352, 270-280
  • (4) Urey et al., 1951, Soc. Am. Bull. 62, 399-416
  • (5) Erez, 2003, Rev. in Min. and Geochem. 54 (1), 115-149
  • (6) de Nooijer et al., 2014, Earth-Science Reviews 135, 48-58
  • (7) Hönisch & Hemming, 2004, Paleoceanography 19, PA4010
  • (8) Henehan et al., 2013, EPSL 364, 111-122
  • (9) Martínez-Botíet al., 2015, Nature 518, 219-222
  • (10) Raitzsch et al., 2018, EPSL 487, 138-150
  • (11) Henehan et al., 2016, EPSL 454, 282-292
  • (12) Louvat et al., 2019, JAAS 8, 1553-1563

How to cite: Buisson, M., Louvat, P., Karancz, S., Tian, R., Raitzsch, M., Bijma, J., and Rollion-Bard, C.: δ11B and B/Ca ontogenetic variability within Globigerina bulloides , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19994, https://doi.org/10.5194/egusphere-egu2020-19994, 2020

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Presentation version 2 – uploaded on 05 May 2020
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  • CC1: Comment on EGU2020-19994, R.Valli Divya, 06 May 2020

    What does the δ11B ontogenetic variability within Globigerina bulloides signifies?

  • AC1: Comment on EGU2020-19994, Matthieu Buisson, 07 May 2020

    Ontogenesis refers to the progressive development of an organism from its conception to its mature form. To investigate the impact of this ontogeny on the boron isotopic ratio of the foraminifera G.bulloides, I measured different size fractions. 

    • AC2: Reply to AC1, Matthieu Buisson, 07 May 2020

      The smallest fraction (250-315 µm) showed a lower δ11B than the highest fractions but after several measurement sessions, this variation became insignificant with the uncertainties. It's more in line with what we know about symbiont-barren species where respiration dominates the microenvironement alteration , in opposition with the symbiont-bearing species,  where the density of the symbionts related to the size changes differently the microenvironment with photosynthesis. 

      • CC2: Reply to AC2, R.Valli Divya, 07 May 2020

        Thank you for the explanation.

        Regards,

        Divya

Presentation version 1 – uploaded on 03 May 2020 , no comments