Coccolithogenesis

Coccolithogenesis is the biological process by which coccolithophores, single-celled phytoplankton, produce and assemble coccoliths. Coccoliths are microscopic calcite plates that form an intricate external skeleton called a coccolithophore. This process is fundamental to the life cycle and ecological role of these organisms.

The formation of coccoliths begins within specialized organelles inside the coccolithophore cell. Calcium ions and bicarbonate are actively transported from the surrounding seawater into these compartments. Within the cell, under controlled conditions, calcite (calcium carbonate) precipitates. This precipitation is not random; it is guided by organic molecules and microtubules that act as a scaffold, dictating the precise shape, size, and crystalline structure of each coccolith.

As coccoliths are formed, they are transported to the cell surface and extruded, where they assemble into the characteristic calcite plating. This deposition creates the protective outer shell. Coccolithophores can shed these coccoliths, and they then sink to the ocean floor, contributing significantly to marine sediments and the global carbon cycle. The study of coccolithogenesis is important for understanding ocean biogeochemistry, climate change, and the evolution of marine life. Variations in coccolith formation can be influenced by environmental factors such as temperature, light, and nutrient availability.