WEBVTT 1 00:00:02.112 --> 00:00:07.048 Coral reefs are one of the richest biodiversities in the world. 2 00:00:07.049 --> 00:00:11.227 These big coral structures have been formed over thousands of years 3 00:00:11.228 --> 00:00:13.108 in the tropical oceans. 4 00:00:14.154 --> 00:00:19.900 The coral has offered shelter to numerous living beings such as fish, mollusks 5 00:00:19.901 --> 00:00:24.602 shellfish, starfish, sea urchins and some algae. 6 00:00:26.406 --> 00:00:28.782 What is coral? 7 00:00:28.783 --> 00:00:33.066 Coral are columns of tiny sea anemones called polyps 8 00:00:33.067 --> 00:00:37.716 which together grow a hard, white central column. 9 00:00:37.717 --> 00:00:39.518 This is their skeleton. 10 00:00:40.773 --> 00:00:46.179 These tiny animals shelter numerous microscopic algae which are indispensable 11 00:00:46.180 --> 00:00:51.613 for the survival of the polyps and hence the development of the coral. 12 00:00:51.614 --> 00:00:54.486 Coral grows in shallow and clear waters 13 00:00:54.487 --> 00:00:58.300 because they need the light which is used by the microscopic algae. 14 00:01:00.600 --> 00:01:03.263 But the coral reefs are in danger. 15 00:01:03.264 --> 00:01:08.540 In fact, because of global warming, the temperature of surface waters has risen 16 00:01:08.541 --> 00:01:12.641 on a long-term basis in certain parts of the oceans. 17 00:01:12.642 --> 00:01:15.567 And when the temperature of the water gets too high 18 00:01:15.568 --> 00:01:19.407 the coral rejects the microscopic algae. 19 00:01:19.408 --> 00:01:23.717 The polyps die and only the white skeleton remains. 20 00:01:23.718 --> 00:01:26.826 This is what is called coral whitening. 21 00:01:26.827 --> 00:01:32.599 Because coral is the essential link in the food chain, its death causes the disappearance 22 00:01:32.600 --> 00:01:37.223 of the animal species living there as well as their predators. 23 00:01:37.224 --> 00:01:41.036 The rich biodiversity of the coral reef is degenerating 24 00:01:41.037 --> 00:01:45.164 in favor of a few species of algae and plant-eating fish.