Coral Reefs and Atolls

Abstract

Coral reefs are calcium carbonate (limestone) structures which are created by colonies of polyps that create a hard exoskeleton (the coral), which then becomes home to zooxanthellae which give the corals their colour. The zooxanthellae and corals live in a rela onship which is mutually beneficial, called a symbio c rela onship. Coral bleaching refers to the loss of the zooxanthellae, reducing the stability of the coral; they also lose their colour. Coral reefs have three main structure types. The first is a fringing reef, which forms along the shoreline of most tropical islands. The Barrier Reef is created through the sinking of land below the sea surface, due to a lack of volcanic ac vity. Lastly the third is an atoll, which is created similarly to the Barrier Reef, but the land sinks quicker, and the reef grows upwards to be near the sunlight.