Scientists solve mystery that some corals change color “when pressed”

Coral bleaching can be devastating to the coral reef system. It occurs when the sea is too hot, causing corals to lose the algae that give them color. Scientists have been studying coral bleaching for years, tracking the extent of damage to coral reef systems and monitoring their recovery. And they noticed something strange and found that the bleached coral reef system didn’t turn white as normal. Sometimes, they get colorful. But why is this happening?

Some corals seem to have a very colorful way to protect themselves, and once the water returns to normal temperatures, they accelerate recovery, researchers J?rg Wiedenmann and Cecilia D’Angelo wrote in The Conversation. At the beginning of their study, they tried to determine why some coral reefs became colorful only when they were bleached, while others became white. They experimented to see if they could replicate this phenomenon in a controlled environment, but at first they couldn’t get any results. It wasn’t until scientists thought about what was going on inside the “overstressed” corals that they found the answer.

“In healthy corals, most of the sunlight is absorbed by algae photochrome,” the researchers explained. “When corals lose algae due to pressure, excess light flows back and forth inside the coral tissue, reflected by a white skeleton. Once conditions return to normal, the algae inside the coral can recover after bleaching. But when corals are illuminated by such light, they put a lot of pressure on the algae and may delay or even prevent their recovery. “

This is bad news, because permanent bleaching can lead to coral degradation and could damage coral reefs that protect the coastlines of continents around the world. It is estimated that if people allow coral reefs to disappear, the damage to coastal areas will be greater than the money we spend to ensure their survival.

However, if corals are only slightly bleached, some species will change color. This seems to be a natural defensive mechanism to cope with rising ocean temperatures or poor water conditions, which we are now seeing more frequently than ever before. “If coral cells can do at least some normal function during bleaching, then increased internal light levels will promote the coral’s production of colorful pigment, protect the coral from light, and form a sunscreen that allows algae to return.” The researchers explained. “When recovering algae begin to reabsorb light for photosynthesis, the level of light inside the coral drops, so the coral stops producing as many of these colored ‘pigments’ as possible. “