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Mg isotopes in biocarbonates

Mg isotopes in biocarbonates. New insights into vital effects associated to echinoderm and bivalve calcification. F. Planchon , J. Hermans, C. Borremans, Ph. Dubois, C. Poulain, Y.-M. Paulet and L. André. δ 26 Mg in Biocarbonates : Introduction. Ca Carbonate. Ca Fluid. Mg Carbonate.

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Mg isotopes in biocarbonates

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  1. Mg isotopes in biocarbonates New insights into vital effects associated to echinoderm and bivalve calcification F. Planchon, J. Hermans, C. Borremans, Ph. Dubois, C. Poulain, Y.-M. Paulet and L. André

  2. δ26Mg in Biocarbonates: Introduction CaCarbonate CaFluid MgCarbonate MgFluid + + Mg/Ca tool KdMg/Ca ≈ DMg = f(T)

  3. δ26Mg in Biocarbonates: Introduction CaCarbonate CaFluid MgCarbonate MgFluid + + Mg/Ca tool KdMg/Ca ≈ DMg = f(T) BioCaCO3 T Proxy Metabolism Age Salinity, etc. Vital Effects From Gaetani (2006), Lear (2002), Elderfield and Ganssen (2000), Mashiota (1999)

  4. δ26Mg in Biocarbonates: Introduction CaCarbonate CaFluid MgCarbonate MgFluid + + Mg/Ca tool ΔCarbonate-Fluid δ26MgBiocarbonate BioCaCO3 ΔInorg-org δ26MgFluid δ26MgCarbonate 26Mg 25Mg 24Mg δ26Mg δ25Mg T Proxy Metabolism Age Salinity, etc. Galy (2001) Vital Effects

  5. δ26Mg in Biocarbonates: Methodology • Sample Purification • Cationic exhange chromatography (Chang, 2003) • Full Mg recovery • Clean techniques

  6. δ26Mg in Biocarbonates: Methodology • Sample Purification • Cationic exhange chromatography (Chang, 2003) • Full Mg recovery • Clean techniques • Analysis • MC-ICP-MS (Nu instrument) • Desolvation (Aridus II) • High sensitivity • 50-100 ng/g • Standard bracketing • Relative to DSM3

  7. δ26Mg in Biocarbonates : Overview Mass-dependent fractionation line Chang (2003, 2004), Wombacher (2006) and Tipper (2006)

  8. δ26Mg in Biocarbonates: Samples • Echinoderms • Starfish • Sea Urchin • Morphology • Culture Exp (T, S) • Bivalves • Clams (Ruditapes Ph.) • Salinity Gradient (2 sites) • Auray River • Shell • Internal fluids • Soft tissus

  9. Echinoderms Sea urchin and starfish

  10. δ26Mg in Biocarbonates : Echinoderms (Starfish and Seaurchin) Coccoliths Inorganic Calcite (theo) Δwater-mineral26Mg: -2.7±0.2‰ Biological effects 0.5 < ΔInorg-org26Mg< 1.5 ‰ Planktonic Forams Galy (2002) Chang (2003, 2004), Wombacher (2006) and Tipper (2006)

  11. δ26Mg in Biocarbonates : Seaurchin Endoskeleton characteristics • Morphological variability • Interambulacral plates record

  12. δ26Mg in Biocarbonates : Seaurchin • Culture experiment (T & S control) • δ26 : f(T) • δ26 : f([Mg]) • Proxy implication • Low metabolism impact

  13. δ26Mg in Biocarbonates : Seaurchin Calcification • Intra-cellular Calcification δ26Mgseawater -0.8 ‰ δ26MgBiocarbonate -2.2 to -2.7 ‰ ACC Metabolism δ26Mgintracell • Equilibrium-like fractionation • Biological mediation • Cell membrane transport • Amorphous phase regulation

  14. δ26Mg in Biocarbonates : Starfish • Low interspecies variability • Moderate biological control

  15. Bivalves Aragonitic Clams (Ruditapes philippinarum)

  16. δ26Mg in Biocarbonates : Bivalves (Clams, Ruditapesphilippinarum) Le Bono Locquemariaquer Poulain (2006)

  17. δ26Mg in Biocarbonates : Bivalves (Clams, Ruditapesphilippinarum)

  18. Conclusions : δ26 Mg– δ25Mg in biocarbonates • New tool to explore biocalcification processes • Identification of mass-dependent fractionation • Potential reservoirs involved • Paleoceanographic Proxy • Direct relationship with T and S • Constrain biocalcification model • Theoretical approach is needed • System evolution (closed-open) • Equilibrium – disequilibrium • Complex mixing model (metabolism, energy consumption, etc.)

  19. Thanks for your attention

  20. δ26Mg in Biocarbonates : Bivalves (Clams, Ruditapesphilippinarum) Adapted from Carré (2006)

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