How did coral polyps help form Tonga's low islands?

The low islands of Tonga’s eastern chain are formed through the biological activity of coral polyps and foraminifera, which are marine organisms that possess calcareous shells. These organisms build rigid coral rock and limestone reefs by secreting calcium carbonate skeletons.12

As these polyps grow, they construct a structural framework that accumulates over time. This process is essential for the islands' existence, as the continuing growth of the coral helps counteract the natural erosion caused by the sea. In some instances, these reef systems have been raised above sea level through geological uplift, creating low-lying, plateaulike islands such as Tongatapu. While these coral formations provide the foundation for the islands, they remain subject to ongoing environmental processes, including weathering and the action of waves.2134