Why is Coral Dying?

Ever since the Industrial Revolution, humans have been contributing to the decline in health of coral reefs. This was the start of the age of technology and inventions that would forever change the way we operate in this world. Unfortunately, many of our inventions alter and harm natural habitats by humans introducing large amounts of toxins or unnatural structures. Most prominently the Revolution jump started Global Warming by raising levels of Carbon  Dioxide in the atmosphere. Other problems related to human industry include sedimentation from coastal developments, and destructive fishing practices from the fishing industry.

Pollution, mainly caused by CO2, creates a few problems for coral reefs. One problem is a process called ocean acidification. This begins with the natural reaction of earth's oceans to regulate global temperatures by intaking CO2. This may sound like a good process, which it is, but since levels are so high in the atmosphere, the ocean is taking in more than what is safe. When more carbon dioxide enters the ocean, the pH of the water changes. Ph is a scale of acidity, and in this case, ocean water is becoming more acidic. Acidic water reduces the availability of carbonate ions to form in water, which aids in shell formation of organisms such as coral, plankton, and shellfish. For coral, their skeletal structures become weaker and provide less of a defense against storms. For the fishing market, if shellfish populations decline, so does the money intake of the industry.

Here is the chemistry of how acidification affects shell formation, from NOAA's PMEL Carbon Program.

Another problem related to pollution is called coral bleaching. This happens because of the sensitivity of coral to a specific range of temperatures.  Rising CO2 levels don't just make the atmosphere warmer, but also the oceans. Reef Relief's article explains how when waters surrounding coral reefs get to high for them to handle, they expel the zooanthellae algae and expose the white skeleton underneath. Since coral cannot survive well without the algae, if temperatures do not fall back into a safe range, the coral polyps will die.

Coral in Process of Bleaching

Sedimentation is the erosion of coastal material ending up in the oceans and covering coral reefs, preventing the polyps from being able to carry out photosynthesis. The biggest cause of high levels of sedimentation is from areas with developed coasts, or coasts where a lot of buildings line the coast. Erosion of the buildings and roads, and unnatural materials like loose plastics carried to the oceans by rain runoff cause the most damage. Coastal developing also allows for the deforestation of mangrove trees and see grasses that act as natural filters for coral reef systems, only to open up new beaches for tourism. Without these habitats, coral's defense against new sediments are very limited.

Overfishing and destructive fishing practices are probably the worst ways in which coral are affected negatively. One fishing technique common to coral reefs is cyanide fishing. This technique involves fisherman squirting cyanide into coral crevices to push out and temporarily paralyze fish that hide in those areas. Not only is this destructive because cyanide is poisonous to the fish, but it also kills the coral and can be harmful to the fisherman if there is accidental exposure.

Cyanide Fishing

Even more destructive may be blast fishing, where dynamite is thrown into the open ocean, killing fish and bringing them up to the surface. In Ron Blythe's educational film "The Fragile Reef: Coral in Peril", blast fishing is documented to occur in areas where coral reefs exist, and the results are terrible.  Blast fishing leaves dead, black coral to line the ocean floor. The coral affected by this can never return, nor can fishermen ever come back to these sights because all life is gone. Why should we do this, if we are lowering the number of fish available for the market?

Blast Fishing

If these activities increase, how much longer are reefs going to survive? When and how are we going to prevent these from taking place? Coral may very well be on its way to looking like this all over the world.

Our Future?

Sources: Threats to Coral Reefs, What Are Mangroves