Coral reefs are a sight to behold. Great coral reefs in the world, such as the Great Barrier Reef in Australia, Belize Barrier Reef in Mexico, Red Sea Coral Reef in the Middle East and the Tubbataha Reef in the Philippines are testaments to the magnificence of natural underwater treasures.

However, coral reefs are also among the most susceptible to environmental destruction. One challenge for the existence of coral reefs is coral reef bleaching.

Coral bleaching is the whitening or fading of coral colors due to the expulsion of the zooxantheallae, a type of a unicellular algae, from the coral system. The zooxantheallae gives the coral reefs its sparkling, gorgeous colors. The loss of zooxantheallae is a sign that the coral reef is undergoing stress, thus a coral reef bleaching occurs. The bleaching signals that environmental imbalance is going on underwater, and the loss of color is the coral reef’s response to these stressors, or imbalance.

Coral reef bleaching is a result of both pathogenic and anthropogenic (human-induced) factors. Pathogenic infection is caused by the bacteria Vibrio Shiloi which is triggered by a marked increase in temperature. Mostly in the summertime, the bacteria unleash heat-sensitive toxins that attack the zooxanthellae in coral reefs.

Human activities contribute to coral reef bleaching. The two major culprits are global warming that induces high sea surface temperature and the increase in solar irradiance that penetrates bodies of water, producing photosynthetical radiation and ultra-violet (UV) light. The thinning of the Earth’s ozone layer and activities like cutting down of trees and destruction of naturally occurring shades enable too much sunlight to penetrate the depths of oceans and seas. Other causes include too much acidity in the ocean, overfishing that destroys marine food cycle and changes in the salinity of seas and oceans, among others.