As you’re probably already aware, coral isn’t just a pretty rock that sits on the ocean floor. Neither is it just a playground for all manner of tropical fish nor is it merely a hunting ground for the predatory ones. Coral is itself a living creature, with all the interesting and novel proclivities that living creatures have. Turns out we can add “color change artist” to the list of neat tricks it can do. Research published in Current Biology shows it’s not just a pretty habitat, those dazzling colors are actually a survival technique. (1) What’s going on here?
Cool Coral Creates Color
It’s a phenomenon known as “colorful bleaching”, and is actually a reaction to a stressful event in the coral’s life. Things like rising ocean temperature, or lack of nutrients may cause this reaction. Researchers from the University of Southhampton believe that these bright neon colors are actually a clever way of trying to find balance again in the coral’s world. The life-giving algae that they depend on are in short supply, and the coral attempts to woo it back with a little razzle-dazzle. (2)
Special Symbiosis
Just as it is on terra firma, it pays to have friends in the sea. You scratch their back, they scratch yours. For coral, that special connection is with minute algae called zooxanthellae. These zooxanthellae live right in the coral’s cells and receive their life-sustaining nutrients from the coral. And thanks to the photosynthesis process that algae are naturally a part of, the coral is gifted with all the plant energy those little zooxanthellae can churn out.
But as you might expect, the balance is tricky. If the water temperature changes even by just one degree, that sweet symbiosis is lost. When the algae die the coral no longer has the food source it depends on, and it turns very white in a process known as “coral bleaching”. (2)
New Color, New Coral
Though it’s a very pale and ghostly-looking white, the coral isn’t necessarily dead. It’s still got some life in it, and it’s even got an idea. By changing color, it can signal the algae to return. This “sunscreen” helps protect the coral’s precious resources and also tells the algae that there’s some yummy photosynthesis that could be happening if it would come back to the party. (2)
While this is a pretty cool trick, it only seems to work if the original event that caused the breakup was minor. The problem is that most stressful events are not minor at all, so a lot of coral is dying. Climate change is certainly no friend of coral’s, and neither is “blast fishing”. Blast fishing is a process by which a huge blast stuns large schools of fish, rendering them helpless and very easy to net. As you might expect, these blasts literally decimate huge swaths of coral reef. Since blast fishing takes place in every part of the world, every part of the world has been losing coral reefs at an alarming rate. (2)
Colorful bleaching is pretty neat, but if coral is to have any real chance of survival, major changes will have to be made to practices like blast fishing. These stress events are not something that they can or should be expected to come back from.
