#Headline Creation Challenge#Grasslands are the foundation of grassland ecosystems, forests are the foundation of forest ecosystems, and corals are the foundation of marine ecosystems.
Throughout the ocean, the proportion of coral reefs is not very high, about 0.25%, but this 0.25% of the proportion is pregnant with more than 30% of marine life, whether fish or arthropods, whether algae or moss, coral reefs can provide them with shelter, food sources and breeding areas, it can be said that coral reef ecosystems are the most biodiverse ecosystems in the ocean and even the world, and the basis of this ecosystem is coral.
Corals look like plants on the surface, but they are actually animals, and huge corals are actually made up of a large number of polyps and calcareous bones.
Although corals are animals, there is a plant living in the coral's body, which is called zooxanthellae. Zooxanthellae do not simply parasitize corals, there is a close symbiotic relationship between them and corals. On the surface, it seems that corals shelter zooxanthellae, but in fact zooxanthellae are feeding corals, and most of the nutrients and oxygen produced by zooxanthellae through photosynthesis are eventually supplied to corals, and zooxanthellae can also absorb waste products generated by coral metabolism.
Although coral is an animal, it is an animal that cannot take care of itself, and it is inseparable from zooxanthellae.
Do zooxanthellae separate from corals? Indeed, this situation is called "coral bleaching". The reason why corals are colorful is actually very related to zooxanthellae, the color of zooxanthellae itself is yellow-brown, so under the illumination of white light, the color of corals is probably also yellow-brown. However, zooxanthellae are very afraid of ultraviolet rays, so when the sun shines down, corals will activate their own fluorescent protein and chromoprotein to protect zooxanthellae to resist ultraviolet rays, so the corals show colorful colors.
The symbiotic relationship between corals and zooxanthellae is not unbreakable, and when the surrounding environment changes adversely, zooxanthellae and corals will separate.
How exactly the separation of zooxanthellae and corals occurs, there is still no clue, we do not know whether the coral expelled the zooxanthellae, or the zooxanthellae actively separated from the coral, the only thing we can be sure of is that once the environment changes adversely, this separation will inevitably occur, and once the separation occurs, the coral will lose its color, from light blue, light pink or white, this phenomenon is called coral bleaching. Coral bleaching does not mean that corals are dead, but they are indeed close to death.
Without zooxanthellae, corals have no food source, and although as an animal, polyps can catch small amounts of food with their tentacles, but it is basically minimal.
If the coral bleachs and the environment can recover within a few months, the zooxanthellae will return again and the corals can gradually return to normal, but if the environment does not improve, the corals will eventually die. After the death of corals, the entire coral reef ecosystem will degrade rapidly, which is arguably the most feared thing for the ocean, considering the position of coral reef ecosystems in marine ecology. So what environmental factors can cause coral bleaching to occur?
Corals have high water temperature requirements, and if the water temperature exceeds 30°C, corals will bleach.
In addition, ocean acidification and marine pollution can also lead to coral bleaching. With the rapid development of human civilization and the continuous advancement of industrialization, the average temperature of the earth continues to rise, and the ocean is naturally not spared, coupled with the ocean's adsorption of carbon dioxide in the atmosphere, the increase in the concentration of carbon dioxide in the atmosphere will aggravate ocean acidification, and marine pollution caused by human activities needless to say, all of which are the causes of coral bleaching. Some scientists predict that by 2030, more than 70% of coral reefs will have bleaching events, which is a terrible thing, but this terrible thing does not necessarily happen, as long as we work together, corals will not lose their color.