This overproduction is heating the planet and the coral reefs have experienced major bleaching because of the rising temperatures. Since 1955, 90% of the atmosphere’s excess heat has been absorbed by the oceans. The annual maximum and minimum temperatures of the oceans surrounding the coral reefs are rising rapidly. It’s increasing with 0.09-0.12°C per decade and is expected to increase with 1-4°C around year 2100. If the temperatures rise to more than 2°C all coral-dominated reef systems will be gone.
Global warming has and is still negatively affecting coral due to the rising temperature of the ocean. The oceans temperature rose 0.18° fahrenheit every decade between 1970 and 2010 due to global warming (Fujita). Even though this doesn’t seem like much of a change, this extra heat makes the sensitive coral more susceptible to illnesses (Le Page 37). The unusually warm waters makes the corals expel food-producing algae which causes the coral to lose its color, turn white, and die due to the lack of nutrition (Markey 1). This is called bleaching (Fujita).
Hich carbon dioxide content in the atmosphere traps heat which is transferred to the ocean; it is also absorbed into the ocen, which causes the ocean to become more acidic. This is the most frequent cause of coral death. In comparison to dynamite fishing, spear fishing, land pollution, sea pollution, tourism, overfishing and invasive species, the increase in greenhouse gasses is the main cause of coral reef destruction globally, as it changes the temperature, current and content of the ocean, and it causes an increase in frequency and intensity of natural disasters. The rise in temperature of the atmosphere causes the sea level to rise as a result of glaciers melting and thermal expansion (1), this causes a change in the density and salinity. This change in density causes currents to vary, becoming more or less violent and varying in temperature (2), causing physical destruction and aiding coral bleaching.
The coral provides a protected habitat for the zooxanthellae and the zooxanthellae provide nutrients that the coral utilizes to survive and thrive. Fertilizer runoff occurs when fertilizer flows over the surface of the land and is carried by rain water into streams, rivers, lakes, and the ocean. Once in the ocean, the nitrogen found in fertilizer is absorbed by algae resulting in large algal blooms and excess macroalgae growth; this process is known as eutrophication (Kroon 1987). The overabundance of algae negatively affects zooxanthellae, and thus coral, because the algae and zooxanthellae compete for resources such as space and sunlight and zooxanthellae need sunlight for photosynthesis (Bell et al., 364). When zooxanthellae do not obtain an adequate amount of sunlight they become stressed and either leave their coral shelter or die (Bell et al., 364).
Corals under stress due to changes in PH levels or temperature of the water will expel the algae (zooxanthellae) living within their tissues causing the coral to turn completely white. This is called coral bleaching. Another cause of coral bleaching is produced formation water, an effluent of offshore oil and gas industries that cause significant bleaching ( White et al .2012) .When a coral bleaches, it is not dead. Corals can survive a bleaching event, but they are under more stress and are subject to mortality. Mortality amongst corals has appeared to be the breakdown of the symbiotic association between the zooxanthellae and the coral host.
Historical View of Coral Bleaching Coral bleaching events have become severe issue in the past twenty years. The increase in water temperatures due to climate change and the increased pollution by humans are some of the main causes of increased coral bleaching events. Coral bleaching is the whitening of the coral due to increased stress. The bleaching process causes the coral to have an increased susceptibility to infections and other external factors. This leads to the ultimate death of the coral and the homes of many sea creatures.
With this in place, the waters become murky and filled with substances that can harm marine life. As mentioned in Cindy Clendenon’s article, Pollution of the Ocean by Sewage, Nutrients, and Chemicals, “coasts are densely populated, the amount of sewage reaching seas and oceans is of particular concern because some substances it contains can harm ecosystems
Coral bleaching has been around for a long time. However, it is more in the recent years the the issue has become so impactful. Now is the time to work towards a solution for coral bleaching before the reefs die, erode, and are gone forever. Scientists have been researching the effect coral bleaching has on marine life, the ecosystem, tourism and the economy. Due to the amount of non-biodegradable
These threats sometimes occurs naturally, however the most significant reason of this damage is human. People cause lots of issues while they are using or even sailing around this entrancing region. One of these issues is over fishing that may disrupt the food chain in the reef. Fishing unconsciously, has an impact on marine life due to using forbidden fishing method, trawling, and to left its trashes such as anchors and nets. In addition to trawling, hunting endangered species is another cause of this threat.