What is Coral Bleaching?
Coral bleaching occurs when coral polyps get rid of the algae that lives inside of their tissues. They will do this when they become stressed. Typically, coral polyps have a symbiotic relationship with the algae and the coral relies on that relationship for survival. This means that the health of the whole reef is dependent on this symbiotic relationship with the algae. The coral is still alive when it becomes bleached, but since the algae provides the coral with about 90% of its energy, once the algae has been expelled the coral will begin to starve. Also without the algae being there the coral is under even more stress which can also lead to its death.
What are the Causes of Coral Bleaching?
The biggest cause of coral bleaching is due to warmer water temperatures. When the water is too warm. Warmer waters is another terrible effect that global warming can have on the environment. More and more coral reefs are becoming bleached and dying because of the increase in ocean temperatures around the world.
Although most coral bleaching events are caused by the water being too warm, there have been cases where this is not true. In January 2010, it was cold water temperatures in the Florida Keys that caused a coral bleaching event. The water temperatures dropped about 12 degrees Fahrenheit lower than they typically were at that time of year. One thing that researchers are looking into is if cold-stress events make corals more susceptible to disease in the same way that warmer waters impact corals.
Ocean acidification is also a cause of coral bleaching. This occurs when carbon dioxide is absorbed into the water, gets converted to carbonic acid, which then acidifies and lowers the pH of the ocean. During this process, carbonate ions bind with hydrogen ions meaning that sea life relying on carbonate to build shells and skeletons have less material with which to do so. Without their shells and skeletons they have no way of surviving.
This is a short video but does a great job explaining what coral bleaching is, what causes it and the effects that it is having!
What Effects is it Having on the Environment?
Almost everything in a coral-reef ecosystem depends on corals or the reef structure in some way. Coral colonies can be a source of food and shelter for many different kinds of organisms and their health is very important to the ecology of the reef community. The negative impacts of coral bleaching and the decline of corals are having detrimental effects on fish communities. Studies have shown that a decline in fish communities usually following declines in coral communities. Also some studies suggest that juvenile fish are more likely to go to areas that have high coral cover because if gives them more protection. With the corals dying, these juvenile fish have less laces to hide and that has a significant effect on the populations.
“Panama Marine Life” By thinkpanama under Flickr
What species are affected the most?
Although there are tons of different species that are negatively affected by coral bleaching, these 5 organisms could become extinct if it gets bad enough.
The first species is the butterfly fish. These fish feed exclusively on coral polyps and with their food source disappearing. their chance of survival is small. Butterfly fish also keep algae from smothering corals and if this population decreases, the corals that are still living could end up dying because of too much algae.
The next species is the spiny lobster. Spiny lobsters need coral reefs for protection, especially when they are molting because that is when they are most vulnerable. These lobsters have a significant role in maintaining a balanced ecosystem. Spiny lobsters are predators of sea urchins, which feed on kelp forests and can destroy them if populations are not predator-controlled.
Dolphins and most whales are predatory animals and they are all carnivorous. They survive by eating fish that rely on coral reef habitats. Every species that is lost from coral bleaching will effect the rest of the ecosystem.
“Dolphins” By joakant Under CC0 Creative Commons
Studies have shown that whale shark populations have decreased in the 1980s and 1990s and this may be due to the destruction of corals. Many corals were destroyed in this time period from people and coral bleaching. Although it is not certain that these two are related to each other, the times frames suggest that they are.
The Hawksbill Sea turtle have become a critically endangered species and are very dependent on coral reefs for their food sources. Their diet mostly consists of sponges. Sea turtles play a very important role in their ecosystems by helping with nutrient cycling from ocean to land, maintaining healthy sea grass beds, and balancing food webs.
“Hawksbill Turtle”By Tchami Under Flickr
What can we do to Prevent it?
There are many ways that people can help reduce the amount of coral bleaching that is occurring. One way that we can do it is by reducing fuel pollution by using alternative transportation methods such as running or biking instead of driving a motor vehicle, or kayaking and canoeing instead of using your boat. Not touching and breaking corals when diving or snorkeling can be a huge help since just touching a coral with your bare hand can have negative effects on it. Not using harmful fertilizers and pesticides in your yard and garden can also help a lot because they will eventually find their way to the ocean. The last way that I will talk about is to volunteer for a community reef and beach cleanup.
“Coral Bleaching” By Klaus Stiefel Under Flickr
Worst Coral Bleached Reefs
The Kiribati reef, the Maldives and the Great Barrier Reef are all suffering the most from coral bleaching as of a study done in 2016. But although these are the worst areas, they are not the only ones. There are many other reefs that are suffering from this too.