Coral bleaching can damage the coral reef system. That happens when the ocean water gets too warm, encouraging corals to lose algae which gives them a lot of color. Humans are largely to blame for this, because warming of ocean temperatures is directly linked to global warming and the impact of humanity on climate, but I digress.
When scientists have studied coral bleaching for years, tracking how much damage has been done to large and small reef systems and monitoring their recovery, they have seen something strange. Sometimes the bleaching reef system does not turn white as usual. Sometimes it looks like it’s covered in a variety of neon highlighter colors. But why?
As written by researchers Jörg Wiedenmann and Cecilia D’Angelo in conversation, it seems that some corals have very colorful ways to protect themselves to speed up their recovery once the sea water returns to normal temperatures.
Their research began by trying to determine why only a few coral reefs became colored during the bleaching episode while others turned pale. Trials are conducted to see whether they can mimic phenomena in controlled settings but initially appear empty-handed. Not until scientists consider what happened in the stressed reef they found the answer.
“In healthy corals, most of the sun’s rays are absorbed by the photosynthetic pigment of algae,” the researchers explain. “When corals lose algae due to stress, excess light moves back and forth within the coral tissue, reflected by a white skeleton. Algae in the reef can recover after bleaching, after conditions return to normal. But when the coral interior lights up like this, it can be very stressful for algae, potentially delaying or even preventing them from returning. “
That’s bad news, because permanent bleaching leads to coral degradation and can destroy corals that protect continental coastlines around the world. It is estimated that the cost of damage to coastal areas if we allow coral reefs to die will be greater than the money we have to pay for ensure their survival. They are important.
However, if corals only experience mild bleaching, some species change color in an effort to encourage algae to return sooner than later. There seems to be some kind of natural defense mechanism for rising sea temperatures or poor water conditions, and we see it more often now than before.
“If coral cells can still perform at least some of their normal functions during bleaching, an increase in internal light levels increases the production of colorful pigments that protect corals from light damage, forming a kind of sunscreen that allows algae to return,” explained the researchers. When the recovered algae begins to absorb light for photosynthesis again, the level of light in the reef drops, so the coral stops producing as much of this colorful pigment as possible. “
