Coral Bleaching Paper Example

Introduction

One of the greatest pleasure when visiting a tropical marine environment is seeing corals. As much as they may look like plants, these oceanic structures are groups of small marine animals within which different species of algae live in giving them a bright color. This algae and coral or coral polyps live endosymbiotic relationship where algae get shelter and protection, and the coral consumes the algae in return (Adipudi et al., 2017). Sadly, because of climate change, world coral reef are increasingly being put under pressure because of coral bleaching. Coral bleaching is a widespread phenomenon that is continuously impacting the world coral reefs and subsequently affecting many organisms living in the oceans, human beings who depend on the seas and industries that utilize coral reefs as their raw material. Corals which are bleached are more susceptible to diseases, have a reduced reproductive capacity, and their growth rate is significantly reduced (Logan et al., 2014). Species that heavily depends on the coral reefs for food and shelter, for instance, some invertebrates and fish are put in great danger when the corals are bleached. This paper will discuss the epidemic of coral bleaching paying attention to the theory related to this issue, the causes, impact, and possible mitigation to this problem.

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Defining of Coral Bleaching

According to Logan et al. (2014) coral bleaching is a phenomenon that transpires when the algae living symbiotically in the coral reef tissues are released making the reefs color to bleach or turn white. Pratchett et al. (2013) on the other hand defines coral bleaching as "the whitening of the coral as a result of the loss of zooxanthellae (algae)" or when the photosynthetic pigment of algae is degraded. Many coastal populations and islands heavily depend on coral reefs for coastal protection, tourist income, and fisheries since corals are biologically reproductive. Coral bleaching comes with many adverse effects since corals forms and maintains islands foundations, sustain diving industries and fisheries and provide a natural barrier against waves. The green algae living inside the coral reefs use water and sunlight to form carbon dioxide and carbohydrates or sugars that feed it while coral reefs eat 90 % of the sugar made (Kemp et al., 2014).

Coral Reefs Formation Theories

Darwin's Subsidence Theory

Darwin took his time to observe the behavior coral reef to determine its possible origin and formation. According to this theory, coral reefs are mostly found in areas where land subsidence have taken place (Grigg, 1982). Darwin claims that, in the beginning, the corals grew as "fringing reef" on the slanted shores of various islands in a narrow tropical sea (Grigg, 1982). The island then began to subside, and the fringing reef was turned into a barrier reef that was detached from the island by a lagoon or a channel of deep water. As the island began to sink, it completely vanished below the ocean surface. According to Van Oppen and Lough (2018) understanding the formation of the coral reefs can assist in developing countermeasures to the increasing cases of coral reef bleaching.

Sir John Murray's Theory of Sea Bottom Rise

Another theory developed on the formation of coral reefs is the theory of sea bottom rise by Sir John Murray in 1875. He added on the view that coral reefs grow entirely on the highest crests of the ocean bottom and that the deposition of residues brings the optimum growth of the reefs (Coelho et al., 2017). His theory supplemented by the ideas developed by Charles Darwin in his subsidence theory.

Review of Literature

Causes of Coral Bleaching

Many factors have been attributed to coral bleaching, but the actual trigger to the release of algae from the coral reefs is yet to be known (Hughes et al., 2017). However, several theories have been developed to explain the root cause of corals bleaching. One is that exposure of corals to high temperature (mostly from climate change) and ultraviolet radiation causes an increase in the enzymatic activity algae making them leave their natural habitat (Depczynski et al., 2013). Two, some evolutionists have theorized that corals have been stressed by many factors meaning that they cannot provide food for the algae and its forced to leave (Depczynski et al., 2013).

According to Heron et al. (2016) bleaching of coral reefs "is as a result of a combination of many factors such as changes in salinity, pollution, sedimentation, increased ultraviolet radiation, excess shade, and disease". However, the major contributor to coral bleaching according to them is the unusually high temperature in the ocean since coral usually flourishes in temperature between 25 and 29 C and a significant increase above this range could be deadly for the coral and the algae (Heron et al., 2016). Van Hooidonk et al. (2014) on the other hand also claims that an increase in temperature contributes significantly to the bleaching of the corals, and the basis of this is a study done on a period of eleven months between 1983 and 1984 when Southern Oscillation El Nino caused a rise in temperature in the Pacific Ocean by 4 degrees. This increase in temperature caused massive bleaching of corals with 72 to 90 % of coral reefs in Galapagos, Costa Rica and Panama perishing (Van Hooidonk et al., 2014).

Warming waters have caused massive bleaching in another region too. One of the largest global coral bleachings occurred in 1998 after El Nino that occasioned many parts of the world killing about 16 % of coral (Ainsworth et al., 2016). Between 2014 and 2016, global coral bleaching occurred as a result of climate change and increase in sea temperature and extraordinary scale of corals were bleached (Ainsworth et al., 2016). The continuous increase in oceanic temperature seems not to stop and this why many scientists believe this is the biggest threat to the lives of corals.

Warm sea waters are not the primary cause of coral bleaching, and according to Bourzac (2018), plastic waste also contributes significantly to the whitening or bleaching of corals. Plastic waste which is 100% from human activities has been found to increase the risk of coral disease from 5 to 90 percent with most of the corals that have had contact with plastics affected mostly Bourzac (2018). The reasons behind this could be one, the corals that interact with plastics waste are more susceptible to stress since plastics can suffocate them and two the plastics could be carrying harmful pathogens that end up killing the corals and the algae (Pratchett et al., 2013). Triggers of Coral Bleaching

Corals have the capabilities to survive short-term instabilities, but if the external factors remain persistent, the algae might have no other option but to leave the coral or it dies off. Even though internal factors can cause bleaching, coral whitening is mainly caused by external factors. According to Jones et al. (2004) some of the triggers of coral bleaching include; increased sedimentation, high solar irradiance (both ultraviolet light and photosynthetic radiation) and overfishing leading to widening of zooplankton and consequent reduction in total oxygen. Other triggers include exposure to chemical spills and oil, acidification of the ocean due to the upsurge of carbon dioxide in the air and presence of pollutants from sunscreen constituents such as enzacamene, Butylparaben, and oxybenzone. Additionally, other triggers can include mineral deposits from dust during the time of drought, amplified sea level, fishing by using cyanide, herbicide, salinity changes, bacterial infections and constant exposure due to long low tide (Logan et al., 2014).

Impact of Coral Bleaching

Coral bleaching has detrimental effects on the ocean surroundings and the ecosystem in general. According to Adipudi et al. (2017), one of the significant impacts of coral bleaching is that it reduces the amount of coral fish significantly. Coral reefs occupy a large portion of the ocean, and many fish depends on them for protection against predators and food. When the coral is bleached, the predator can easily see the fish, and the food that was being manufactured by the algae is gone meaning the number of fish will decrease. A man also depends on this fish, so the existence of the coral affects the life of human beings (Adipudi et al., 2017).

Moreover, herbivorous fish, damselfish and other poly-consuming butterfly fish will lose their natural habitat and food when the coral decolorizes (Kemp et al., 2014). Done et al. (2003) noted that the number of fish living in the coral reefs decreased when the coral was destroyed because of bleaching. Done et al. (2003) also argues that coral reefs are single most important species in the ecosystem in the oceans and they also expand their reach to outside organisms that depend on the seas.

In regions where coral reefs were abundant, macroalgae and turf algae have taken over causing a mix of a different number of fishes (Van Hooidonk et al., 2014). Such takeover leads to significant changes within the habitats and biodiversity may be lost. Coral reefs have a natural way to maintain biodiversity within the oceans as they contribute to nutrient recycling and primary production (Hiatt & Strasburg, 1960). Reduced biodiversity leads to loss of some rare species that may be important to other organism or even to man.

Majority of communities that live around the coastal regions rely heavily on coral reefs. Coral reefs are a significant tourist attraction bringing enormous income for countries that heavily depend on tourism for their GNP (Graham & Nash, 2013). As climate change continues to take over the world and global temperature continue to increase, more corals are bleaching and dying meaning that tourists will not visit those countries such as Australia that relies on tourism and generates billions of dollars each year from this industry (Van Hooidonk et al., 2014).

Fishing is another industry that relies heavily on the existence of coral reefs. Fish get most of their nutrients from the coral's reefs in the oceans and more than a quarter fishermen are known to get their fish from the corals (Graham & Nash, 2013). What this means is that billions of people who eat fish depend on the corals and many enterprises have been built of fish from the corals (Graham & Nash, 2013).

Coral reefs act as coastal protection for many humans living near the coastal lines (Adipudi et al., 2017). They protect humans against wave action and storm damage and in the process protecting beaches which are essential economically, communities, and coastal cities. Bleached corals reefs are much weaker compared the healthy and productive corals and are unable to sustain constant pressure from the ocean meaning that at one time storms and wave action can cross the coastal lines causing a disaster (Kemp et al., 2014). Moreover, humans do use coral reefs for other purposes such as to manufacture medicines that relax muscles, reduce inflammations, and kill particular viruses.

Coral Bleaching Mitigation Methods

The impacts the coral bleaching has on human and marine life are certainly bright and is therefore crucial to have proper mitigation approaches to this issue. Corals are naturally resilient with some characteristics such as high recovery rates, tolerant and resistant, screening, shading, an...