Coral Reef Bleaching: The Epidemic That Is Killing Oceans

The ocean covers 71 % of the earth’s surface and is home to over a million different species. Within this unique underwater world are coral reefs. Coral Reefs are underwater ecosystems, formed of colonies of small marine animals coral polyps, held together by calcium carbonate. These ecosystems protect ocean environments from the damaging effects of wave actions and tropical storms, that provide habitats for nearly one-fourth of marine organisms, and even extend advantages to humans and other land life. Coral reefs can be located in the shallow parts of tropical water, because their tissues require photosynthesis and warm temperature (NOAA). Coral Reefs are often known to be called, “The cities of the sea” because of the diversity each ecosystem has within it. Many coral reefs have symbiotic relationships with a variety of organisms that give protection from predators in order for a habitat and nutrients. Although coral reefs only make up a very small percentage of the ocean surface, they are vital to not only the ocean’s environment but the entire biosphere.

Coral Bleaching Explained

Conservation of Coral Reefs is important as numerous threats face them including increasing temperatures from global warming, ocean acidification, overfishing, and pollution. All of which can lead to coral bleaching and the death of enormous coral reefs. Coral bleaching occurs when coral polyps lose their symbiotic algae or “zooxanthellae” which causes their living tissue (which provides color) to become transparent allowing you to see the stony skeleton which is white, hence the name “coral bleaching”. Many factors can contribute to this but without their necessary tissue, coral reefs are more susceptible to starvation, disease, and predators.

Abiotic Factors

A variety of abiotic factors lead to coral bleaching, however, biotic factors such as human activity may impact abiotic factors so biotic factors are indirectly involved. Temperature extremes are the most common cause of coral reef bleaching. When temperatures dramatically drop or increase over a short period of time bleaching is almost always seen. Additionally, extreme exposure to Ultraviolet Rays from the sun have also been linked to bleaching as the symbiotic algae coral contains has very specific conditions it needs to thrive in. When the pH or other conditions of the water the coral is living in in altered by pollutants and other waste products bleaching ensues. Any type of environmental stress put on coral and its symbiotic algae will often times cause severe coral bleaching which can lead to death.

Biotic Factors

Severalin of these abiotic factors are impacted by biotic factors. Human activity contributes to the changes in temperature, water composition, and ultraviolet ray exposure and adds stress to coral reefs. Zooxanthellae are living organisms who have their own set of conditions ideal for survival, when the location of the coral has conditions that are no longer suitable, the algae is expelled from the coral tissue. This occurrence is due to the changes above which are caused mostly by humans. Coral mining by humans for souvenirs and other purposed causes stress to reefs causing them to be more vulnerable. Global warming, which causes an increase or decrease in water temperature is also blamed for bleaching which humans have been proven to contribute to. On top of that, waste produced by the population that is dumped in the ocean, especially close to shores where coral reefs are most commonly found, can disrupt the natural conditions of the water and add inorganic materials disrupting the pH and causing coral reef bleaching.

Ecological Relationships

Coral reefs are ecosystems that rely on a number of organisms to thrive, a healthy reef has lots of marine life that contributes to a productive community. Nutrient cycles are important to coral reefs as well and the disruption of these can cause coral reef bleaching and even death. Zooxanthellae plays an important role in the nutrient recycling and use in coral reefs. It processes nutrients and “fixes” carbon through photosynthesis essentially “feeds” it to the host coral. In return the algae receives the waste nutrients of the coral. When concentrations of Carbon Dioxides, Phosphorus, Nitrogen, and Oxygen are disrupted by non-natural activity (Human Activity) Zooxanthellae can’t maintain a symbiotic relationship with reefs causing them to leave while the host dies.

Management Considerations

The death of coral reefs is plaguing the aquatic ecosystem and it is our responsibility to do something about it. Coral Bleaching is a preventable phenomenon. Efforts to reduce global warming by minimizing greenhouse gases are important. Water pollution can be reduced by less dumping of waste on the shores by large companies and reducing any runoff. Additional management strategies include preservation methods by establishing areas protected by the government and mainly In Situ conservation methods. Human’s choices in our ecosystem have effects on the entire biosphere so we need to be aware when we make unhealthy decisions for our planet.