Coral bleaching occurs when one of four things happens; changes in ocean temperature, runoff and pollution in the water, overexposure to the sun, or extremely low tides. All of these situations cause the coral to get stressed. When the coral get stressed bad enough, they can starve or become diseased. While recovery is possible, death is often the end result. So what causes coral to become stressed?
First, stress can happen due to any of the four situations listed above, ocean temperature change, runoff or pollution, too much sun, or very low tides. Since all of these things can occur at any given moment, it is hard to find ways to prevent it. Ocean temperatures have been on the rise since the 1980's causing, so far, three global coral bleaching events. We are currently in a global coral bleaching event that started in 2014 and has been continuing since then, causing massive coral death.
Runoff and pollution will always be a factor for the world since we have been living in this industrial age of new inventions, less natural resources, and more inversion than ever. As for overexposure to sunlight and low tides, these go hand in hand. The tides will go in and out many times throughout the day which can expose coral to the air above. While this is good for the birds, who can now catch the fish, the coral can become stressed if the tides stay out for too long. So how does the bleaching process actually occur?
Coral bleaching is when the animal expels algae (zooxanthellae) from its tissues. Coral need the algae because it provides food by making carbohydrates through the process of photosynthesis so that the coral can eat. This is why starvation is an issue when bleaching occurs. Since the algae has been kicked out, the coral's colors leave with it, giving it the 'bleached' appearance. All of the vibrant colors we recognize and associate with coral are the living bits of algae in the tissues of the coral.
Thus, without the algae, the skeleton of the coral is exposed. If it has been exposed for too long, this is when starvation and diseases set in. No carbohydrates equals no food. No outer layer equals no defenses, leaving the coral weak against outside bacteria, therefore allowing infection to spread more easily. As stated beforehand, recovery is possible but only if the algae return soon enough to provide for the coral. If the algae does not return, the coral's remaining tissues fall away and soon after algae will cover the skeleton once again.
Many people wonder, why is this important? Coral bleaching is bad for the coral but also affects humans as well as marine life. While reefs are only 0.1% of the ocean floor, they provide shelter to 25% of all marine species. They also protect shorelines by providing a buffer against waves, storms, and floods. This buffer helps stop property damage, erosion, and loss of life. When the reefs have been destroyed or damaged by coral bleaching, the coastal communities suffer. That is just one way their deaths affect humans. Another is that coral reefs support the fishing industry, tourism, and have shown to be useful in the medical field. Scientists' studies of the coral reefs show that they can help treat many diseases such as cancer, arthritis, bacterial infections, Alzheimer's disease, heart disease, and viruses.
Since there have been such high death rates in the past few years for coral, the medical use and research of them could be halted or even stopped. Due to this, there have been many conservation acts made to help restore and protect the reefs. Since the reefs have been on the decline, scientists worry that they won't be able to uncover all of the benefits of these reef systems before they disappear. “An estimated 95 percent of the world’s oceans remain unexplored, so it’s possible that we might lose significant marine organisms without ever knowing they existed in the first place,” explains Stephanie Wear, a marine scientist on the Conservancy’s Global Marine Team. “A devastating loss of biodiversity could mean that fewer species will be around for future medicinal research and biomedical studies.”
All in all, coral bleaching is a terrible thing that happens within the earth's reefs but part of it seems to be natural since the tides will always go in and out, the sun will always since, and humans aren't going anywhere fast in terms of stopping runoff and pollution in the ocean. It's great that there are organizations working to educate people around the world about our precious reef systems and that one day we could be curing many of the human race's most serious and common medical ailments.
