Under a stress provoking environment—changes of temperature, light, or nutrients—, corals expel algae out and turn completely white. This is called coral bleaching, a process that happens at an alarming rate today. According to the National Oceanic and Atmospheric Association, 75% of the world's tropical coral reefs between 2014 and 2017 experienced heat-stress that could trigger bleaching. When corals’ colors fade away, there's devastating damage not only to corals itselves, but the whole ecosystem. 

Broadly speaking, the main cause of coral bleach is climate change. The hot weather warms the temperature of the ocean, which is a change corals are vulnerable to. Even a rise of two degrees farenheit can cause corals to lose their color. Another factor that triggers the process are runoff and pollution. When harmful chemicals from agriculture or from rain which picks up pollutants on the ground reaches the ocean, the water ends up with an overgrown algae and sickened corals. 

Regardless of whether the coral survives or not, there is a lifelong impact on them. If the stressor stays for long, it dies. Even if coral survives through the process, it will have difficulty reproducing and therefore, the whole ecosystem is left affected. Numerous animals, for instance the sea turtles, jellyfish, and shrimps, need coral reefs to survive, the bleaching indicates a breakdown of their “community.” Besides this, there are other damages that result: loss of the reef barrier that stops storms and decline in coral tourism. 

Coral bleaching is caused by us, humans, and the marine ecosystem is another difficulty that is threatening their life. Small steps starting from using tumblers or picking up trash floating on the ocean could help. The responsibility to resolve this problem is not only on scientists or the Department of the Environment, but on every individual living on earth. We contribute to climate change without even noticing it; it is time to acknowledge it and change ourselves to do more green actions. 

Referance:

https://oceanservice.noaa.gov/facts/coral_bleach.html

https://www.worldwildlife.org/pages/everything-you-need-to-know-about-coral-bleaching-and-how-we-can-stop-it

https://www.vancouverislandfreedaily.com/news/university-of-victoria-study-shows-ocean-warming-depleting-coral-reef-fish-communities-by-half-7194126

https://coral.org/en/blog/corals-innovative-approach-to-resolving-stormwater/