Unveil the mechanism of biomineralization in coralline red algae through nano diffraction: precursors, phase stability, and phase compositio

Coralline red algae are marine calcifiers that precipitate CaCO3 during their life in both calcite and aragonite phases with variable Mg
content. These sediments constitute the habitats for several ecosystems (i.e. coral reef) and are endangered by ocean acidification; thus representing an urgent and relevant iissue. The Mg/Ca ratio is an established temperature proxy for climate reconstructions. At the macro-scale, the growth reveals a banding pattern, with fluctuations in Mg/Ca related to seasonal fluctuation; at the micro-scale, the skeletal parts show specific ultrastructures (i.e. in the different calcified layers in the cell walls). It is still not clear how biomineralization and Mg incorporation take place. We propose the spatially resolved diffraction investigation of five samples of coralline red algae at the micro and nanoscale. The goal of the proposed experiment is to disclose the mechanism of the biomineralization, cast light on the actual Mg distribution and its role.