Coral Field Guide

Hard corals have limited tolerance to changes in physical parameters like salinity, temperature, and rate of sedimentation. They also require light to support the photosynthetic activities of their symbiotic algae. They need a hard substratum to settle on. 

In Hong Kong, the coastal environment is usually characterized by limited amount of hard bottom, so space for settlement could be scarce. Competition for space among corals and between corals and other organisms is intense. Besides, coral colony itself could be used by boring organisms as habitat.

These organisms bore and live inside the coral skeleton. They easily settle on the corals surface and attack the corals especially when corals are not in good health. Extensive infestation of coral colony by these borers can cause the coral skeleton to become so weakened that it can easily be toppled by strong waves generated during a storm. Many predators, like snails and some nudibranch, can also feed on coral polyp.

Similar to other places of the world, corals in Hong Kong are threatened by human activities. These threats include: 

• Coastal development
• Over-exploitation and destructive fishing practices
• Inland and marine-based pollution
• Intense recreational use
• Boat anchor and abandoned nets / garbage