Advanced analysis of coccospheres : towards a better understanding of their hidden functionalities

Coccolitophores are abundant unicellular phytoplanktons that produce calcium carbonate exoskeletons. They are major players in the carbon cycle. They live in surface layers of the sea, where they use light to photosynthesize, fixing CO2 into organic matter leading to a decrease in dissolved CO2 in the ocean. Coccolithophores produce calcite (i.e. CaCO3) in the form of minute platelets called “coccoliths”. These platelets are formed by tiny elements so well-entangled that they confer to the coccoliths their integrity. The main issue of this proposal is to unravel the shape of these elements with a resolution better than 10nm so that we could unravel how they act as self-blocking agents. In addition as a challenging test experiment, we want to study (if time permits it) frozen coccospheres to understand how the protococcoliths are formed inside the membrane of the coccospheres. We expect to image the nucleus on which protococcoliths are formed.