Mg isotopes in biocarbonates

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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
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d26Mg in Biocarbonates Introduction
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d26Mg in Biocarbonates Introduction
From Gaetani (2006), Lear (2002), Elderfield and
Ganssen (2000), Mashiota (1999)
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d26Mg in Biocarbonates Introduction
?Carbonate-Fluid
?Inorg-org
Galy (2001)
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d26Mg in Biocarbonates Methodology

• Sample Purification
• Cationic exhange chromatography (Chang, 2003)
• Full Mg recovery
• Clean techniques

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d26Mg 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

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d26Mg in Biocarbonates Overview
Mass-dependent fractionation line
Chang (2003, 2004), Wombacher (2006) and Tipper
(2006)
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d26Mg 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

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Echinoderms

• Sea urchin and starfish

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d26Mg in Biocarbonates Echinoderms (Starfish
and Sea urchin)
Coccoliths
Inorganic Calcite (theo) ?water-mineral26Mg
-2.70.2
Biological effects 0.5 lt ?Inorg-org26Mg lt 1.5
Planktonic Forams
Galy (2002)
Chang (2003, 2004), Wombacher (2006) and Tipper
(2006)
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d26Mg in Biocarbonates Sea urchin
Endoskeleton characteristics

• Morphological variability
• Interambulacral plates record

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d26Mg in Biocarbonates Sea urchin

• Culture experiment (T S control)
• d26 f(T)
• d26 f(Mg)
• Proxy implication
• Low metabolism impact

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d26Mg in Biocarbonates Sea urchin Calcification

• Intra-cellular Calcification

d26MgBiocarbonate -2.2 to -2.7

• Equilibrium-like fractionation
• Biological mediation
• Cell membrane transport
• Amorphous phase regulation

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d26Mg in Biocarbonates Starfish

• Low interspecies variability
• Moderate biological control

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Bivalves

• Aragonitic Clams (Ruditapes philippinarum)

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d26Mg in Biocarbonates Bivalves (Clams,
Ruditapes philippinarum)
Le Bono
Locquemariaquer
Poulain (2006)
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d26Mg in Biocarbonates Bivalves (Clams,
Ruditapes philippinarum)
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Conclusions d26 Mg d25Mg 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.)

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Thanks for your attention
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d26Mg in Biocarbonates Bivalves (Clams,
Ruditapes philippinarum)
Adapted from Carré (2006)