Coral bleaching today is an environmental warning that tiny animals called polyps are in danger of dying, or already have. Coral bleaching is an indication of the health of the ecosystem that makes up a coral reef. Coral bleaching often is the result of higher/lower water temperatures or an increase in sunlight. Other sources impacting could be the result of an increased acidity level in the water. Over fishing has effected the coral reef's delicate balance, as has silt run-off and changes to the actual salinity of the water.
Within the coral reefs exists one of the finest examples of a symbiotic relationship where two forms of life are interdependent upon each other for health and vitality. Creatures called polyps create the actual calcium carbonate structures one sees in the coral bed and the minute algae called zooxanthellae provide the polyps with the balance required including oxygen.
Coral bleaching is the result of polyps being over stressed. They actually eject the zooxanthallae from their membranes. The percentages of rejection can be anywhere from 60-90%. In turn this affects the zooxanthellae whose ability to photosynthesize decreases dramatically. Without this balanced symbiotic relationship, bleaching occurs.
The zooxanthellae actually are the color makers of coral, and splash them with the colors of reds, oranges, and blues and so forth. Polyps are colorless and the microscopic algae provides for their color living in their tissues. A short time period for these ejections will not kill the polyps, however, longer periods of time and the polyps will die.
Many stress factors are the result of man's mishandling of the environment, some occur naturally. Coral reef bleaching can also continue even if the source of the stress has been eliminated. Coral does have some species of polyps that are hardier than others, and coral reefs have been known to recover, but this process takes weeks, months and often years.
Coral bleaching is a major concern to environmentalists. Those who watch global warming are concerned about both lower and higher water temperatures. Coral polyps can be affected by as little as a couple of degree difference and begin to stress and the bleaching occurs shortly after. There are actually world wide virtual stations to monitor color bleaching. There are 24 stations world wide that constantly monitor the health of coral reefs to trigger alarm when factors in those areas are affecting the coral reefs and bleaching is occurring. As of the day of this article, Oman and Belize are under careful watch.