Coral Reef Formation: How Calcite Skeletons Build Underwater Structures

Yes, coral reefs grow through the accumulation of calcium carbonate (calcite/aragonite) skeletons secreted by coral polyps.

Process

1. Living polyps extract dissolved calcium and carbonate from seawater.
2. They deposit it as a hard exoskeleton beneath their soft bodies.
3. When a polyp dies, its skeleton remains.
4. New polyps settle on the old skeletons, building upward and outward.

Result

Over centuries to millennia, this creates massive reef frameworks that support 25% of marine species.

The process is biologically mediated but geologically significant—reefs are among the largest biological structures on Earth.