Diapositive 1 - de l'UniversitÃ© libre de Bruxelles

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Chapitre IVwater molecules, which creates a strong hydration sphere around the ion and poisons thegrowing calcite surface (Raz et al 2000). Sulphate ion, by forming strong ion pairs withmagnesium, reduces the hydration of the latter (Kralj et al 2004). This facilitatesmagnesium incorporation into growing calcite crystal and could result in simultaneoussulphate incorporation as an impurity in the mineral phase.In conclusion, strong correlations between skeletal Mg/Ca and S/Ca ratios wereevidenced in the calcitic skeleton of different echinoderms and hypercalcified spongespecies. We hypothesise that this correlation is due to the magnesium chelating propertiesof sulphates in solution, leading to a parallel incorporation of both elements in themineral. Even if sulphur co-occurs in organic and mineral skeletal phases, our resultsshowed that it is principally located in the mineral phase.AcknowledgementsThe authors wish to thanks Ph. Pernet, J. Navez, L. Monin and N. Dakhani for thespecimen analyses. T. Dupont provided technical support. R. Manconi and F. Ledda madepossible sample collection in Sardinia. This work was supported by a “Plan Action 2”grant (contract n r WI/36/F02), a “David and Alice Van Buuren” grant, the CALMARS IIproject from the Belgian Federal Science Policy, Brussels, Belgium (contract n rSD/CS/02A) and FRFC contract (n r 2.4532.07). Ph. Dubois is a Senior ResearchAssociate of the National Fund for Scientific Research (FRS-FNRS Belgium).92
Chapitre VCHAPITRE VRelative influences of solution composition and presence of intracrystalline proteinson magnesium incorporation in calcium carbonate minerals: insight into the vitaleffectsJulie Hermans 1&2 , Luc André 3 , Jacques Navez 3 , Philippe Pernet 1 and Philippe Dubois 1∗In preparationABSTRACTBiogenic calcites may contain considerable magnesium concentrations, significantlyhigher than those observed in inorganic calcites. Control of ion concentrations in thecalcifying space by transport systems and properties of the organic matrix ofmineralization are probably involved in the incorporation of high magnesium quantities.However, the relative effects of the magnesium and organic matrix concentrations in theprecipitation solution on magnesium incorporation into calcite have never beenquantified. In the present study, we performed in vitro precipitation experiments atdifferent Mg/Ca ratios in the solution (Mg/Ca solution ranging from 1:1 to 5:1) in presenceof soluble organic matrix macromolecules (SOM), extracted from sea urchin tests andspines, whose skeletal magnesium concentrations are respectively 9.8 and 3.4 mol%MgCO 3 . Amino acid analyses showed that test SOM were richer in Asx and Gly. HR-ICP-MS measurements of the precipitated minerals showed that, at a constanttemperature, the magnesium incorporation is mainly dependent on the Mg/Ca solution ratio.However, a significant increase in magnesium incorporation was observed in presence ofSOM compared with control experiments. Furthermore, test SOM induced a higherincrease than spine SOM. We suggested that this specificity could be linked to the relativeabundance of aspartic acid rich proteins in the amino acid assemblage. Proteinconcentration also influenced the magnesium concentrations in the in vitro precipitatedminerals. According to SEM observations, amorphous calcium carbonate was precipitatedat high Mg/Ca solution . The observed predominant effect of Mg/Ca solution , probably mediated∗ 1Marine Biology Laboratory (CP 160/15), Université libre de Bruxelles, 50 Avenue F.D. Roosevelt, B-1050, Belgium2Department of Invertebrates, Royal Belgian Institute of Natural Sciences, 29 Rue Vautier, B-1000, Belgium3 Section of Petrography-Mineralogy-Geochemisty, Royal Museum of Central Africa, 13 Leuvenstesteenweg, B-3080 Tervuren,Belgium93
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UNIVERSITÉ LIBRE DE BRUXELLES (ULB
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RemerciementsJ’aimerais tout d’
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Ce travail a été rendu possible p
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Dans la seconde partie, la modulati
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higher magnesium concentrations pre
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DEUXIÈME PARTIE: Processus minéra
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Introduction généraletransitoire
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Introduction généraleFigure 2 : C
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Introduction généralemajoritairem
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Introduction générale2.2.1 Facteu
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Introduction générale2.2.2 Facteu
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Introduction générale2.2.2.4 Effe
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Introduction généralemacromolécu
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Introduction généralemagnésium e
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Introduction généraleFigure 8 : R
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Introduction générale3.1.2 Le mag
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Introduction généraled’une nich
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Introduction généraleFigure 11 :
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Introduction généralecroissance c
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PREMIÈRE PARTIEFACTEURS ENVIRONNEM
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Chapitre ICHAPITRE IGrowth rate and
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Chapitre I1998). Rosenheim et al (2
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Chapitre ITable 4: Dates of transfe
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Page 57 and 58: Chapitre ITable 5: Skeletal Mg/Ca a
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Page 61 and 62: Chapitre IICHAPITRE IITemperature,
Page 63 and 64: Chapitre IIeffects of climate chang
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Page 67 and 68: Chapitre IIFigure 18: Skeletal Mn/C
Page 69 and 70: Chapitre IIFigure 19: Mg/Ca ratio i
Page 71 and 72: Chapitre IIor a magnesium compartme
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Page 75 and 76: Chapitre IIICHAPITRE IIISalinity ef
Page 77 and 78: Chapitre IIIcontrolled aquarium con
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Page 81 and 82: Chapitre IIIbetween these different
Page 83 and 84: Chapitre III2.6Skeletal Sr/Ca (mmol
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Page 87 and 88: Chapitre IIIIon transport in echino
Page 89: DEUXIÈME PARTIEPROCESSUS MINÉRALO
Page 92 and 93: Chapitre IVINTRODUCTIONBiogenic cal
Page 94 and 95: Chapitre IVAfter collection, the se
Page 96 and 97: Chapitre IVratioed against backgrou
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Page 100 and 101: Chapitre IVTable 15: Probabilities
Page 102 and 103: Chapitre IVFigure 29: FTIR spectra
Page 104 and 105: Chapitre IVFigure 31: XANES spectra
Page 108 and 109: Chapitre Vin vivo by ion transport
Page 110 and 111: Chapitre VSea urchins produce an in
Page 112 and 113: Chapitre Vwere surrounded with cond
Page 114 and 115: Chapitre V3535Mineral Mg concentrat
Page 116 and 117: Chapitre VMorphology of in vitro pr
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Page 122 and 123: Chapitre Vproject from the Belgian
Page 124 and 125: Discussion généraleDans cette dis
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Page 128 and 129: Discussion généralede régulation
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Page 132 and 133: Discussion générale3. Perspective
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Page 136 and 137: Références bibliographiquesAmeye
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Page 140 and 141: Références bibliographiquesDustan
Page 142 and 143: Références bibliographiquesHartma
Page 144 and 145: Références bibliographiquesKolesa
Page 146 and 147: Références bibliographiquesMagdan
Page 148 and 149: Références bibliographiquesQuamme
Page 150 and 151: Références bibliographiquesRosenh
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Références bibliographiques142
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Annexestempérature salinité indiv
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AnnexesANNEXE 2Tableau 20: Rapports
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Annexes
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