【明報專訊】◆What? Corals are animals?!

Yes! They are made up of tiny animals called polyps (珊瑚蟲). Corals can be categorised as soft corals, which are joined by soft tissue (軟組織), and hard corals, which connect their limestone skeletons (碳酸鈣骨幹) to make up colonies. Hard corals can build up reefs over centuries.

Some corals have a mutualistic (互利共生) relationship with a type of tiny algae (水藻). This means they both rely on and benefit from each other. Corals provide shelter for algae, in return the algae provide corals with colours, as well as oxygen and food from photosynthesis (光合作用). Some corals have tentacles to capture planktonic (浮游的) animals or even small fish.

◆Where do corals live?

Whilst most corals live in shallow waters in tropical (熱帶) and subtropical (亞熱帶)regions, some survive in cold, deep waters or even near the polar regions. Providing food and shelter for about 25% of all ocean species, coral reefs are diverse ecosystems (生態系統) and are often called "rainforests in the sea". Coral fishes can be found in many forms and colours, alongside with different invertebrates (無脊椎動物) such as shrimps, crabs or octopuses around the reefs. In Hong Kong, corals are found in the eastern and northeastern waters, such as in Hoi Ha Wan, Yan Chau Tong and Tung Ping Chau Marine Parks. Over 80 species of hard corals have been recorded, supporting around 350 species of fish.

◆Conservation work in Ocean Park

In collaboration with the Swire Institute of Marine Science of the University of Hong Kong (HKU-SWIMS), Ocean Park is breeding and growing local species of hard corals, such as Acroporidae (鹿角珊瑚科), for education and research. Aquarists collect data from their growth, their environment, and observe their interaction with other corals. As coral growth can be affected by many factors, the aquarists have to monitor them closely so as to ensure their health.

◆Why are corals declining?

Greenhouse gas emission leads to rising temperature. When seawater becomes too warm, the algae would leave the coral polyps. Losing colours and food source, the corals become white and very weak. This is known as "coral bleaching" (珊瑚白化) and is threatening corals around the world. As corals are essential for many marine animals, the loss of corals would mean the decline of many other lives.

You can also help protect corals. Save energy to reduce greenhouse gas emission in your daily life!

- Switch off and unplug electronic appliances after use.

- Use fans instead of air conditioners.

- Enjoy sports, reading, painting or meeting friends. Explore more ways to have fun without electricity!

■Glossary

tentacle(n) 觸手

diverse (adj) 多樣的

breed (v) 繁殖

interaction (v) 交流; 相互影響

[Smarties' Power English 第201期]