| environ. |
barrier reef An elongated accumulation of coral lying at low-tide level parallel to the coast but separated from it by a wide and deep lagoon or strait. The coral is thought to have formed initially on a flat surface: then as the sea-level rose in post-glacial times, thereby submerging the irregular wave-cut platform, the coral growth kept pace with the rising ocean level, so creating the great thickness witnessed today in such places as the Great Barrier Reef off the East coast of Queensland, Australia. This stretches for more than 1900 km and varies in width from about 30 km to 150 km; coral reef Coral reefs have been built up from the skeletons of reef-building coral a small primitive marine animal, and other marine animals and algae over thousands of years. They occur in clear, shallow and sunlit seas. Coral reefs are one of the most productive and diverse ecosystems and are estimated to yield about 12% of the world's fish catch. They are very vulnerable to any change in their environment, especially pollution, because it makes the water opaque. They must have light in order that photosyntesis by the algae can take place. Like trees, corals reflect the environmental conditions in which they grow, indicating marine pollution, sea-surface temperature and other aquatic conditions |
