What is Coral Bleaching?[edit]

Coral reefs are one of the most diverse ecosystems in the world that are affected tremendously by a variety of alterations that are occurring known as the "Rainforests of the Ocean". Coral reefs occupy less than one percent of the ocean floor but are the home to many marine animals and over 4,000 fish on its own. Coral reefs provide resources to over 500 million people in over 100 countries in the world and are great for the economy. Unfortunately, coral reefs are in great danger due to coral bleaching. Coral bleaching occurs when corals are presented with very stressful and harm conditions like temperature, light, or nutrients that causes them to expel symbiotic algae that live in their tissues resulting them to turn completely white. Corals are healthy when a brownish tone is evident, but when a white tone is shown this is a sign of the bleaching that has occurred. Coral and algae depend on one another in order to survive and give off that healthy brown tone in a symbiont relationship, but when these corals are stressed the algae are forced to leave causing a change in color. When corals are bleached it doesn’t mean they have died, they can survive the stress they experience through coral bleaching, but they are more susceptible to becoming vulnerable and mortality in the long run.Evidence shows that oceans are warming due to the rise in temperature that for the most part are due to greenhouse gases resulting from humans; an example of an anthropogenic disturbance. Corals, unfortunately, do not do well in very warm or cold waters since they release the algae (zooxanthellae) that live in their tissues. The different impacts include warming oceans, sea level rise, changes in storm patterns, changes in precipitation, altered ocean currents, and ocean acidification^[1]. The influences combined, impact the services coral reefs provide.

Coral bleaching has occurred at a large scale all around the world. One major event of coral bleaching occurred in the United States where the Caribbean in 2005 lost more than half of its reefs. The ocean water centered in northern Antilles near the Virgin Islands and Puerto Rico was too warm for the coral reefs that lead to extreme thermal stress^[2]. The thermal stress was recorded to be so large compared to all the stress of the previous 20 years combined. Another case of coral reefs being greatly affected happened near the Florida Keys where a large amount of corals died when the water temperatures dropped way to low that this cold- stress event lead to many different corals being impacted^[3]. Thus, coral bleaching can occur at temperatures at either ends of the spectrum, too hot or too cold.

Global warming is mainly known for rising temperatures, but along with the rising temperatures causing coral bleaching cascading events like changes in wind patterns, jet streams, and water circulation are occurring. If humans continue to mine and burn coal causing a release of carbon pollution into the air which is heating the Earth and warming the oceans. It was thought for a long time that the main cause for coral bleaching brought about direct anthropogenic effects like water pollution and sedimentation, but evidence has shown that anthropogenic global climate changes have dominated. About 50%-70% of these global climate changes are directly affecting these reefs which including the rising in temperature, increasing oceanic CO₂ (ocean acidification), changes in ice cover, salinity, oxygen levels, and circulation. Research has shown that over the years there has been an increase of 1°C to 3°C in sea surface temperature that has led to the mortality of so many reefs^[4]. For example, the reefs in Guam in the past 40 years have declined from 50% in 1960 and 25% in the 1990’s. If these types of patterns continue, coral reefs will reach mortality quickly. Not only is coral bleaching affecting species diversity, but it is depleting resources that provide millions with medicine, food, protection, and funds from fishing and tourism. Approximately 99 reef countries exist that provide resources to about six million fishermen^[5]. Overall, climate changes are causing the degradation of coral reefs leaving these species to be greatly endangered and put in danger resources utilized by humans. Overall, climate changes are causing the degradation of coral reefs leaving these species to be greatly in endangered and harming what is thought of by many people as the most biodiverse ecosystem on earth^[5].

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