| 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 | 珊瑚礁 (珊瑚礁由一种小的原始海生动物礁珊瑚的骨骼和其他海生动物及藻类历经几千年而形成。它们出现在清澈而有阳光照射的浅海里。珊瑚礁是最具生产力和种类最繁富的生态系统之一；据估计，全世界的鱼获量有百分之十二来自珊瑚礁。它们非常容易受到环境中任何变化的伤害，尤其是污染，因为污染会使得水体变成不透明。它们必须有光，藻类的光合作用才能进行。像树木一样，珊瑚反映了它们生长环境的状况，显示了海洋污染、海面温度和其他水体的状况。) |
