Jessie Rizk, Sarah Corbin, Austin Krupar, and Macy Tetrick
Coral reefs are important to marine life for so many reasons. They house many different species and play an important role in the marine food chain. For example, plants, prey, and predators can all call coral reefs home and provide each with shelter. Without the coral reefs as their home, prey would have nowhere to hide and would throw the food chain out of balance. Coral reefs also play a big part in protecting humans around the shoreline and sustaining our economy. Coral reefs take the biggest hit from large waves, storms, and floods. This lessens the damage that property would otherwise have without coral reef. As for our economy, there are so many different kinds of fish that live near coral reefs, therefore, many commercial and local fisheries rely on it for this large fish population. From the US alone, coral reefs are responsible for about $100 million from fisheries. Another reason that coral reefs are important to our economies is because it is a tourist attraction. Locations that have coral reefs on their shoreline gain so much money by supporting different activities like scuba diving, snorkeling, and glass bottom boating near coral reefs. It is a beautiful underwater sight which can allow local economies to boost from the revenue they receive solely based on these coral reef activities.
Coral reefs are found all over the world in warm waters. Mostly found near the equator, over half the world’s reef populations are found in Australia, Indonesia, Philippines, Papua New Guinea, Fiji, and the Maldives. They are made of three components: a hard surface, coral polyps, and reef animals. A hard surface is often a submerged rock but could be any submerged hard surface. Coral polyps are tiny animals that are related to anemone and jellyfish. These grow and reproduce to form layers of coral. Lastly, reef animals contribute to the health and function of a reef. There are different types of coral reefs. The most common is the fringe reef. This is the kind that grows near coastlines. There are also barrier reefs, atolls, and patch reefs. These mainly vary by depth and size. Coral reefs need to be in warm, clean water with a healthy wildlife population to survive and reproduce. Water that has been polluted by runoff or overfished will not allow for corals to reproduce.
Corals are in the kingdom animalia and phylum cnidaria. Thus, they are closely related to jellyfish, sea anemones, and hydroids, all of which also occupy the same phylum. Like all cnidarians, anatomy of coral polyps is relatively simple, with one opening into the stomach that acts as both the mouth and as a way to excrete waste. Surrounding this mouth is a ring of tentacles at the coral used for defense and capturing prey items. Furthermore, some groups of coral secrete calcium carbonate skeletons that form the foundation of coral reefs, with their hard skeletons providing many species of marine life with shelter. Corals have a complex endosymbiotic relationship with zooxanthellae, a group of symbiotic dinoflagellate algae commonly found in marine water. Zooxanthellae can be obtained via vertical transmission in which zooxanthellae is placed within the coral egg from the parent. However, horizontal transfer of zooxanthellae is more common, in which zooxanthellae is engulfed by the coral from the environment. Zooxanthellae are stored within the cells lining the coral’s stomach in special structures called symbiosomes. While inside the coral cell, the zooxanthellae continues to produce photosynthate like sugars and amino acids, up to 95% of which is transferred to the host coral. In return, the coral provides the zooxanthellae with metabolic waste that the algae needs in order to grow including nitrogen, carbon dioxide, and phosphorus. However, under conditions of extreme stress, this symbiotic relationship can break down, resulting in the loss of photosynthetic pigment or zooxanthellae altogether. This phenomenon is known as bleaching (picture below depicts a healthy coral on the left and a bleached coral on the right). With the increasing average temperature due to the increase in carbon emissions from the industrial revolution, there has been a large increase in the thermal stress corals regularly experience, leading to mass bleaching events around the world.
Clearly, coral reefs have impressive adaptations and responses. This translates into their defense mechanisms as well. Coral reefs essentially have two types of defenses: chemical and physical. Toxins are their main chemical defense and have evolved over many years to become one of their greatest assets. The toxicity levels of each reef fluctuate depending on their surrounding environment, level of predation, etc. If a reef has high levels of nutrition, it is likely that this specific reef does not experience much predation. If, suddenly, the coral reef is preyed on more than usual, it will begin to adapt by decreasing its nutrient levels in order to make itself less “desirable” for predators. If a coral reef has low nutrient levels already, it would be safe to assume that the reef is preyed on often. Along with advanced chemical responses, the coral reef has developed impressive physical defenses as well. On the ends of each coral tentacle contains stinging cells, or nematocysts. These nematocysts are used to sting, capture or kill prey. Reefs also emphasize the “survival of the fittest” concept by “fighting off” other reefs for desired space.
As discussed earlier, coral reefs play a huge role in human life as a food and economic resource. However, coral also presents a multitude of medicinal benefits for humans. The “underwater pharmacy” has provided medicinal components from bone grafts to antiviral drugs to anticancer agents. The calcium carbonate is a key material in a lot of bone grafts, and it has been proved to be even better quality than ceramic. Coral reefs have also been used to produce HIV treatments like Zidovudina, antiviral drugs like Ara-A that are used to fight RNA tumors, and Ara-C anticancer agents used to fight leukemia, breast and liver cancer. As if that wasn’t enough, coral reefs also possess a protective enzyme called secosteroids. Secosteroids are utilized by coral reefs to fight off their own infections, similar to our own immune system. Researchers have discovered a way to extract the secosteroids and convert them to fight off human infections like asthma, arthritis, and other inflammatory issues amongst humans.
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