Coral reefs have been called the rainforests of the ocean and are one of the most diverse and important ecosystems on the planet. This paper will explore how global warming has effected these fragile ecosystems. It will focus on the impact of increasing ocean temperatures on coral reefs.
Coral reefs exist globally from 30N to 30S latitude and have existed in some form on Earth for over 200 million years. Over 2500 species of coral have been identified 1000 of which are reef building hard coral. Reefs are actually limestone structures produced by small animals called coral polyps. These polyps contain unicellular plants (algae) called zooxanthellae in their tissue. They have a symbiotic relationship which means, "living together." During the day the zooxanthellae rise to the surface of the animal and produce food by photosynthesis. At night the polyp extends a stinging, multitenticled mouth that feeds on any planktonic animals. They both benefit from the waste products of the other. They also work together to capture calcium carbonate from seawater and convert it into the hard limestone structures in which they live. Because corals survive due to this fragile relationship, they are very sensitive and tolerate relatively narrow ranges of water temperature, salinity and transparency.
Coral reefs are estimated to cover less than .2% of the ocean floor but contain approximately 25% of the ocean’s species. They provide protection for shorelines, reducing erosion. They also give food, shelter and protection to almost one million marine species and act as a nursery for growing fish. Humans benefit directly from coral reefs. They supply us with food, jobs (through fishing and tourism) and serve as a source of medicine.
1955 Temperature Anomalies
(Degrees C variation from Average Temp.)
1994 Temperature Anomalies
As more and more greenhouse gases are being emitted into our atmosphere, the Global Mean Temperature is rising. Because the specific heat of water is relatively large, much of the excess energy is being stored in the Earth’s oceans. As more of the sun’s energy is retained by increasing greenhouse gases, the earth’s oceans are heating up. This can be seen by an increase in average water temperature and warm water anomalies (water temperature over the average).
Coral bleaching occurs when coral polyps are stressed. One form of stress on the coral is an increase in temperature. Often a one degree Celsius elevation in the monthly mean maximum temperature is enough to cause bleaching. Bleaching is the process of the coral polyps expelling the zooxanthallae. The polyps are left without any pigmentation and appear nearly...