When one pictures a dream vacation, their mind typically wanders to a tropical beach paradise with soft white sand that fills the spaces between their toes, water so clear they can see the sea floor, along with the thousands of beautifully bright colored fishes swimming among vibrant coral reefs. Though many know of coral reefs, it is not commonly understood that coral reefs are living colonial creatures. Though this wonderland covers less than 1 percent of the entire globe, they are one of the most diverse ecosystems known to mankind, second only to tropical rainforests. In a sense, reefs are the rainforests of the ocean. Even more astounding, these reefs have an immense value to humans medically, economically, as well as environmentally.
Coral reefs are composed of thousands of polyps, and understanding their composition is key to knowing how they connect to the rest of the world. Now, a single polyp as shown in Figure 1 is composed of an opening- the mouth- covered by the tentacles, which are used for defense as well as catching food. Within the tentacles are nematocysts, cells used to sting any foreign creature presenting a danger. This is similar to the way a jellyfish would sting, as they also have nematocysts in their tentacles. Yet, one of the most important cells that live within the tissue of polyps are tiny plant cells known as zooxanthellae. Zooxanthellae are photosynthetic algae, which coexist with coral through a mutualistic relationship. Mutualism, also known as symbiosis, is a relationship where both parties benefit from each other; it’s a win-win situation.
So the question is raised, how does coral benefit from these algal plant cells? Basically, coral acts as the bodyguard. It provides a home, protection for this delicate cell, as well as compounds needed for photosynthesis, and in return it receives a myriad of advantages. As a recompense, zooxanthellae will remove waste, produce oxygen, supply the necessary nutrients for the creation of calcium carbonate -what the skeleton is composed of- , and give coral astonishingly beautiful colors. Since this algal cell is photosynthetic, it must be constantly exposed to sunlight, which is why coral is commonly in shallow waters near the equator, where the most sunlight is provided. The equatorial area is a utopia, because the sunlight radiating through allows for warm waters.
Though this ecosystem appreciates warm waters, it is very selective, in that it can only tolerate a slim difference of temperatures ranging from 23-29℃, as well as a certain pH. Unfortunately, climate change due to anthropogenic -or human- causes, is making it extremely difficult for coral to adapt to their rapidly altering environments. Currently, ⅓ of coral reefs are at risk of extinction, and are constantly in danger due to both global and direct threats. When regarding climate change, “ninety-seven percent of publishing climate scientists agree that global climate change is real and a result of human activity. By reducing the human use of fossil fuels, we can curb carbon dioxide emissions (CO2), slow the pace of climate change and give coral reefs the critical time they need to adapt” (Coral Reef Alliance).
Global Threats include three major categories: climate change, ocean acidification, and ozone depletion. Climate change is due to an increase of carbon dioxide (CO2), which comes from an excessive burning of fossil fuels. Trees absorb around 25% of that carbon dioxide, while oceans absorb about another 30%. The other 45% of this heat trapping gas remains in the atmosphere and air we breathe. Because this compound is heat trapping, the Earth’s temperature increases, causing glaciers to melt and sea levels to rise. This rise in sea level means coral is deeper underwater. When coral is too deep underwater, this prevents the proper amount of sunlight to reach zooxanthellae, leading to difficulty in proper growth.
Rising levels of carbon dioxide also cause warmer waters and increased acidity. Natural disasters such as hurricanes, typhoons and tsunamis originate from warm waters, so larger amounts of CO2 dramatically increases the frequency of natural disasters, as well as strengthens them. Absorbed CO2 will also increase the acidity of oceans. Acidity is regulated by the pH scale, so when the ph lowers further than the coral’s preference, calcification rates decrease, meaning weaker skeletons, a higher vulnerability to coral disease, destruction by storm, and death. Degradation of coral in shallow water also results from excessive UV radiation. As CO2 interacts with other anthropogenic/ozone destroying compounds such as CFCs, which come from everyday products like air-conditioning or refrigerators, the situation is only exacerbated leading to further ozone loss. A thinner ozone layer will increase the amount of UV radiation that comes onto the planet.
As for direct threats, unsustainable overfishing, water pollution, and habitat destruction only further endanger this ecosystem. Overfishing lessens the amount of necessary algae grazers. If too much algae grows, the balance is disrupted and it will smother reefs. Too little fish also means decreased economic stability and decreased food security for local towns. There are also destructive forms of fishing such as bottom trawling which will drag heavy nets across the ocean floor, destroying everything in its path in efforts to catch as many fish as possible. As for water pollution, it is largely land based, and the runoff will include sewage, fertilizer, and pesticide. These sediments will then flow into the ocean, further increasing algal growth, and threatening the billions of dollars that come from tourism.
Moreover, what exactly is the importance of coral reefs to humans? One of the most present reasons this ecosystem benefits us is medically. The biodiversity within this little world is crucial to finding to medicines and cures to diseases. Drugs have already been created to be used for treatment of cancer, arthritis, bacterial infections, and other viruses. In addition, they play an immense role for providing economic and environmental services worth up to $375 Billion per year. Through tourism and fisheries, the income will stack up quickly. Yet one of the most valuable services they provide is protection against natural disasters. As mentioned previously, global increase in CO2 emissions and rising temperatures will only further intensify occurrences such as tsunamis. These giant structures have a great strength, and play a big role in protecting shorelines against harmful waves. This protection prevents billions of dollars in property damage, and huge loss of human life.
Developed countries are a massive reason as to why the climate is changing- particularly China and the U.S. As shown in Figure 2, the U.S. is second in regards to largest producers of CO2 emissions worldwide. This begs the question, why doesn’t the government do something to reduce these emissions? Well, from their perspective, seeing money now and upfront which stems from industry, is the most important matter. Figure 2
The Paris Climate Agreement was a huge step forward for Americans, as it placed restrictions on industry to reduce the releases of greenhouse gases. Though with Trump’s decision to withdraw from the Paris Agreement, the future of coral reefs and the environment does not look bright.
Though this is a complex and large scale issue, there are still many ways in which an individual may contribute to the salvation of this diverse habitat. For one, living sustainably and reducing one’s carbon footprint helps immensely. Using compact fluorescent light bulbs, planting trees to prevent runoff, using organic pesticides, reducing amounts of airplane trips, and buying energy efficient cars are all very doable. Being a smart consumer comes in handy also, as eating sustainable seafood will discourage overfishing. Reducing the amount of trash one produces through using reusable lunch containers, using compost bins, as well as using reusable grocery bags aids in reducing the amount of waste that ends up in the ocean. Finally, becoming an advocate for this planet through calling and emailing government officials would be an amazing tactic toward saving and ecosystem that cares so much for everyone.