Strong kinetic effects on Sr/Ca ratios in the calcitic bivalve

Anne Lorrain (1, 2) , David Paul Gillikin (3) , Yves-Marie Paulet (1) , Laurent Chauvaud (1) , Alain Le Mercier (1) , Jacques Navez (2) , Luc André (4)

1 LEMAR - Laboratoire des Sciences de l'Environnement Marin (LEMAR)
2 Musée royal de l'Afrique centrale
3 VUB - Vrije Universiteit Brussel
4 RMCA - Royal Museum for Central Africa [Tervuren]

Although Sr/Ca ratios in abiogenic calcite are strongly controlled by precipitation rates, such a kinetic effect has never been demonstrated in calcitic bivalve shells. Therefore, we report Sr/Ca ratios together with daily growth rates in the calcitic shells of 4 individuals of the bivalve Pecten maximus (age class I). Ratios of Sr/Ca were found to be variable among individuals that grew at the same location, illustrating that vital effects dominate over environmental controls. Although daily growth rate was correlated with shell Sr/Ca ratios, it explained only half of the Sr/Ca variations. However, daily shell surface area increment, an estimation of the total quantity of carbonate precipitated for a given time, explained 74% of the Sr/Ca variability in the shells of P. maximus. This proves, for the first time in a calcitic bivalve, that shell Sr/Ca partitioning is mainly controlled by kinetic effects. The Sr/Ca ratio should therefore be tested as a potential proxy of calcification rate in modern or fossil calcitic biocarbonates.

Domains: Environmental Sciences

Anne Lorrain, David Paul Gillikin, Yves-Marie Paulet, Laurent Chauvaud, Alain Le Mercier, et al.. Strong kinetic effects on Sr/Ca ratios in the calcitic bivalve. Geology, 2005, 33 (12), pp.965-968. ⟨hal-00452403⟩