Coral reef bleaching is when zooxanthellae, single-celled microscopic organisms that give corals their color, are released by the corals in an effort to control the amount it contains. This process is normal until too much zooxanthellae are released. The excessive amount released causes coral reefs to lose their color and die off.
Coral reef bleaching is occurring worldwide. It is occurring in places like Panama(70%), Mexico(40%), Puerto Rico, British Virgin Islands, Texas(35%-100%), and even more extensively in the Caribbean.
Hypothesis, Predictions and Experiments
There are many hypothesis that explain the cause of coral reef bleaching. Some of them are:
H1. Global Warming
Global warming causes water temperature to increase which causes corals to release their algae. This causes bleaching.
A. Predictions- Bleaching will occur in corals that are exposed to warmer water temperature
B. Experiments- control group =corals exposed to a healthy growing environment; experiment with various water temperatures to see at what temperature bleaching will occur. If bleaching occurs as water temperature increases then global warming is a cause of coral bleaching.
H2. Over-fishing and other fishing practices.
Over-fishing and other fishing practices exposes reefs to a stressful environment causing bleaching to occur. Fishers often use huge nets to catch more seafood. These nets cause reefs to break. In addition, over-fishing reduces the amount of sea creatures needed to maintain the healthy environment of the coral reefs.
A. Predictions- If I run a huge fishing net over a healthy population of corals reefs this will cause their environment to be stressed and bleaching will occur.
B. Experiments- Perform experiment in a healthy coral environment. Run a huge net over this population of corals. Also, eliminate most of the sea creatures vital to the maintenance of the coral reefs. If over-fishing and other fishing practices are a cause bleaching will occur.
The absorption of carbon dioxide from the atmosphere causes the oceans ph to decrease or acidify. This causes algae to die off. These algae are needed to aid in the building of coral reefs and in effect provide a habitat for the creatures needed to maintain their health.
A. Prediction- If Carbon Dioxide is introduced to an unstressed coral reef population bleaching will occur.
B. Experiment- Increase the level of Carbon Dioxide in a healthy coral reef habitat. If acidification is a factor bleaching will occur.
H4. Inorganic nutrients
A high amount of Inorganic nutrients attracts more zooxanthelae. These algae give coral reefs their color. If there are too many the corals will secrete more causing bleaching.(“Coral Reef Bleaching”, by Jason Buchheim)
A. Predictions-If I increase the amount of inorganic nutrients in a healthy coral reef environment zooxanthalae will increase and cause bleaching to occur more rapidly.
B. Experiments- eliminate or reduce the amount of inorganic nutrients in coral reef environment, along with stressors that influence coral bleaching. Also, increase the amount of Inorganic nutrients in another coral reef group excluding environmental stressors that cause bleaching. If increasing Inorganic Nutrients is a factor, bleaching will occur.
H5. Exposure to Air
Significantly low Tides, sea level drops due to el Nino, or the elevation of land can expose corals to the surface.
A. Predictions- Exposing coral reefs to the atmosphere will cause bleaching to occur.
B. Experiment- Expose an unstressed population of coral reefs to the earth’s surface. If exposure to air is a cause bleaching can be observed.
Sedimentation has also been used as a hypothesis to the cause of coral reef bleaching. However, there is not enough evidence that suggests that it is the sole cause.
The debate about the cause of coral reef bleaching goes on and on. However, what is certain is that something must be done to correct the problem.