Calcidiscus is a single-celled protist and a type of haptophyte, a group of microscopic algae that live in the ocean and make food through photosynthesis. Like many haptophytes, it produces chalk-like plates made of calcium carbonate, but Calcidiscus is known for making especially large and sturdy ones. When these organisms die, their plates sink to the ocean floor, contributing to sediments such as chalk and limestone and playing a key role in regulating the Earth’s carbon and climate.
| Genus |
Key Features |
Role in the Ocean |
| Calcidiscus |
Produces especially large and sturdy chalk plates (coccoliths) |
Major contributor to marine sediments like chalk and limestone |
Emiliania
(Emiliania huxleyi) |
Most abundant coccolithophore, small plates, forms massive blooms visible from space |
Huge influence on the carbon cycle, helps cloud formation through sulfur compounds |
| Gephyrocapsa |
Plates are bridge-shaped (name means “bridged capsule”) |
Important in past climate records, useful for dating ocean sediments |
| Coccolithus |
Produces large, flat plates with a central hole |
Long fossil history, key indicator in paleoclimate studies |
| Helicosphaera |
Plates are spiral-shaped (like a screw) |
Adds diversity to coccolith shapes in sediments |
| Florisphaera |
Forms basket-like coccoliths |
Contributes to fine structure of marine carbonate sediments |