Decoupled carbonate chemistry controls on the incorporation of boron into Orbulina universa
| Type | : | ACL |
|---|---|---|
| Nature | : | Production scientifique |
| Au bénéfice du Laboratoire | : | Oui |
| Statut de publication | : | Publié |
| Année de publication | : | 2017 |
| Auteurs (9) | : | HOWES Ella,louise KACZMAREK K RAITZSCH M MEWES A BIJMA Nienke HORN Ingo MISRA Sambuddha GATTUSO Jean-pierre BIJMA J |
| Revue scientifique | : | Biogeosciences |
| Volume | : | 14 |
| Fascicule | : | |
| Pages | : | 415-430 |
| DOI | : | 10.5194/bg-14-415-2017 |
| URL | : | - |
| Abstract | : | In order to fully constrain paleo-carbonate systems, proxies for two out of seven parameters, plus temperature and salinity, are required. The boron isotopic composition (δ11B) of planktonic foraminifera shells is a powerful tool for reconstructing changes in past surface ocean pH. As B(OH)4− is substituted into the biogenic calcite lattice in place of CO32−, and both borate and carbonate ions are more abundant at higher pH, it was suggested early on that B ∕ Ca ratios in biogenic calcite may serve as a proxy for [CO32−]. Although several recent studies have shown that a direct connection of B ∕ Ca to carbonate system parameters may be masked by other environmental factors in the field, there is ample evidence for a mechanistic relationship between B ∕ Ca and carbonate system parameters. Here, we focus on investigating the primary relationship to develop a mechanistic understanding of boron uptake. Differentiating between the effects of pH and [CO32−] is problematic, as they co-vary closely in natural systems, so the major control on boron incorporation remains unclear. To deconvolve the effects of pH and [CO32−] and to investigate their impact on the B ∕ Ca ratio and δ11B, we conducted culture experiments with the planktonic foraminifer Orbulina universa in manipulated culture media: constant pH (8.05), but changing [CO32−] (238, 286 and 534 µmol kg−1 CO32−) and at constant [CO32−] (276 ± 19.5 µmol kg−1) and varying pH (7.7, 7.9 and 8.05). Measurements of the isotopic composition of boron and the B ∕ Ca ratio were performed simultaneously using a femtosecond laser ablation system coupled to a MC-ICP-MS (multiple-collector inductively coupled plasma mass spectrometer). Our results show that, as expected, δ11B is controlled by pH but it is also modulated by [CO32−]. On the other hand, the B ∕ Ca ratio is driven by [HCO3−], independently of pH. This suggests that B ∕ Ca ratios in foraminiferal calcite can possibly be used as a second, independent, proxy for complete paleo-carbonate system reconstructions. This is discussed in light of recent literature demonstrating that the primary relationship between B ∕ Ca and [HCO3−] can be obscured by other environmental parameters. |
| Mots-clés | : | - |
| Commentaire | : | - |
| Tags | : | - |
| Fichier attaché | : | - |
| Citation | : |
Howes EL, Kaczmarek K, Raitzsch M, Mewes A, Bijma N, Horn I, Misra S, Gattuso J-P, Bijma J (2017) Decoupled carbonate chemistry controls on the incorporation of boron into Orbulina universa. Biogeosciences 14: 415-430 | doi: 10.5194/bg-14-415-2017
|