The major role played by calcification in climate control and in geological modelling is enough to justify the choice of this theme. Calcification, together with respiration and photosynthesis, is one of the main mechanisms controlling the concentration of carbon dioxide, the principal greenhouse effect gas, in our atmosphere. Biomineralization is also a key process in several other domains: human health (osteogenesis, orthopedic surgery …), and chemistry of materials (biomaterials).

In spite of the major importance of biomineralization, biological mechanisms which transform ions in solution into a mineral structure are still largely unknown. Whether of animal or vegetal origin, the biomineral contains an organic fraction, the organic matrix, whose role, largely controversial, seems to be to control the first stages of nucleation and the special form (macro- and micro-) of the structure. However this organic matrix is still little understood and has only been studied in a few zoological groups (sea urchins, molluscs, crustaceans, vertebrates).

Our work is mainly focused on corals. These are actually responsible, together with the calcareous algae (coccolithophores) and the foraminifers, for 99.9% of the calcareous deposits on the surface of the globe. So, a better understanding of biomineralization processes in marine organisms should allow for a better understanding of the biogeochemistry of carbon and calcium.
In addition, these organisms (corals, calcareous algae and foraminifers) have one common property: they all photosynthesize either directly (coccolithophores), or indirectly due to symbiosis with unicellular algae (foraminiferans, corals). Light strongly stimulates calcification: we say photo-calcification ("light-enhanced calcification"). However, the relation between these two processes is under discussion: does it involve provision of energy, elimination of CO2 and other metabolic toxins, or the synthesis of indispensable elements in the make-up of the skeleton (organic matrix?).

On the other hand, coral skeletons provide recordings of physicochemical conditions (temperature, CO2 concentration, nutriments) which prevailed at the time of their deposition, they are qualified as environmental archivists. Interpretation of this information by paleoclimatologists, in the same way as is done in polar ice and in the core of trees, should allow for a better prediction of climatic evolution. But how can the reading be done if the alphabet is not understood? No good interpretation can be made yet, because not enough is known about the biomineralization process.

Interest on this subject is not limited to environmental sciences but also extends to the biomedical domain. Our results throw a new light on the mineralization mechanism, a common phenomenon from invertebrates to man (bone and tooth formation, notably). Several of these biominerals are also commercially important, such as the axial skeleton of red coral or oyster pearls. It is strange to note that the biochemical composition of these biominerals is still unknown today.