Coral Bleaching
June 4, 2014

Coral Bleaching

Have you ever seen a coral reef in person? If not, I cannot recommend doing so highly enough. They are incredibly beautiful works of nature. I would also recommend doing so sometime soon, as sadly these magnificent structures are disappearing fast. Unfortunate considering that somewhere around 500 million people across the world rely on them as a source of protein and for coastal protection. Not only that, but coral reefs bring in billions of dollars annually in both the fishing market and tourism. Yet in the Caribbean alone, the coral reefs have deteriorated by more than 80 percent in the last century and this trend does not appear to be stopping any time soon.

Corals depend on single-celled algae that are a part of them. These algae provide their nourishment and are what gives them their vibrant colors. Many of these species of algae are very sensitive to heat, however, and as the ocean temperatures continue to rise it causes the reefs to expel these algae from themselves in what is commonly called coral bleaching.

Hoping to understand this phenomenon, a team of researchers from the University of Georgia led by Dustin Kemp, a postdoctoral associate in the UGA Odum School of Ecology, have been studying the Orbicella faveolata, more commonly known as the mountainous star coral, and the various symbiotic algae found within. Mountainous star coral is one of the major reef-building types of coral in the Caribbean and, while common, it has a rather unique trait. That being that while most coral has just one type of symbiotic algae, Orbicella faveolata commonly associates with up to four at once, some of which are more heat-tolerant than others.

Kemp and his colleagues took samples from all six coral colonies for the past few years, including samples of before, during, and after a bleaching event. This allowed them to compare the communities of symbiotic algae from these periods and see how the coral handles the change. What they found was that before the event, these corals contained three different types of algae, two of which were more tolerate to heat. During the event, the heat-sensitive algae were much less prevalent as they were being expelled – which was as expected – and after the event, the heat-tolerant algae had taken over the parts of the coral the less tolerant algae used to occupy. According to Kemp, “The corals didn’t die after this bleaching event, they recovered – and that’s good, that’s important – but there could be potential tradeoffs associated with the shift to heat-tolerant algae. That question of tradeoffs is what we’re working on now… We know that increased ocean temperatures are one of the major threats to coral reefs worldwide. So understanding coral-algae dynamics, and how different algae can handle increased temperature, is important to see how the whole ecosystem will be affected by this environmental perturbation.”

Hopefully, what Dustin Kemp and his team discover will lead to new ideas on how to protect and preserve our coral reefs, one of the greatest natural treasures our world has to offer. Despite only covering 0.1 percent of the sea floor, coral reefs serve as the habitat for somewhere between 25 and 35 percent of all oceanic fish. Loosing them would be a harsh blow to our ecosystem that I do not know if we could recover from.

Image Credit: Thinkstock

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