Control of aragonite deposition in colonial corals by intra-skeletal macromolecules

• Main Authors: Falinii, G., Reggi, M., Fermani, S., Sparla, F., Goffredo, S., Dubinsky, Z., Levi, O., Dauphin, Y., Cuif, J.P.
• Other Authors: Dpto di Chimica "G. Ciamician", Alma Mater Studiorum Università di Bologna = University of Bologna (UNIBO), Dpto di Farmacia e biotecnologie, Dpto di Scienze Biologiche, Geologiche e Ambiental, Department of Life Sciences, The Mina & Everard Goodman, Bar-Ilan University Israël, Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Lophelia pertusa
• Online Access: https://hal.science/hal-00824951

International audience Scleractinian coral skeletons are composed mainly of aragonite in which a small percentage of organic matrix (OM) molecules is entrapped. It is well known that in corals the mineral deposition occurs in a biological confined nucleation site, but it is still unclear to what extent the calcification is controlled by OM molecules. Hence, the shape, size and organization of skeletal crystals from the fiber level through the colony architecture, were also attributed to factors as diverse as nucleation site mineral supersaturation and environmental factors in the habitat. In this work the OMs were extracted from the skeleton of three colonial corals, Acropora digitifera, Lophelia pertusa and Montipora caliculata. A. digitifera has a higher calcification rate than the other two species. OM molecules were characterized and their CaCO3 mineralization activity was evaluated by experiments of overgrowth on coral skeletons and of precipitation from solutions containing OM soluble and insoluble fractions and magnesium ions. The precipitates were characterized by spectroscopic and microscopic techniques. The results showed that the OM molecules of the three coral share similar features, but differ from those associated with mollusk shells. However, A. digitifera OM shows peculiarities from those from L. pertusa and M. caliculata. The CaCO3 overgrowth and precipitation experiments confirm the singularity of A. digitifera OM molecules as mineralizers. Moreover, their comparison indicates that only specific molecules are involved in the polymorphism control and suggests that when the whole extracted materials are used the OM's main effect is on the control of particles' shape and morphology.