Introduction

Coral reefs around the world are in danger. One of the causes is global warming, which has been increasing the temperature of the ocean water resulting in coral bleaching. This web page will focus on damage occurring to the Great Barrier Reef.
 

What is a Coral Reef?

A coral reef is a ridge formed in shallow ocean water by accumulated calcium-containing exoskeletons of coral animals, certain red algae, and mollusks. Coral reefs are tropical, forming only where surface waters are never cooler than 20° C (68° F).

The only difference between a barrier reef and a coral reef is that a barrier reef occurs farther offshore, with a channel or lagoon between it and the shore.

The outer layer of a reef consists of living animals, or polyps, of coral. Single-celled algae called zooxanthellae live within the coral polyps, and a skeleton containing filamentous green algae surrounds them. The photosynthetic zooxanthellae and green algae transfer food energy directly to the coral polyps, while acquiring scarce nutrients from the coral. The numerous micro habitats of coral reefs and the high biological productivity support a great diversity of other life.
 

The Great Barrier Reef

The Great Barrier Reef is a chain of coral reefs in the Coral Sea, off the northeastern coast of Australia.  The largest reef in the world, it extends about 1250 mi from Mackay, Queensland to the Torres Strait (between Australia and New Guinea.)
The Great Barrier Reef is home to a remarkable number of organisms. The coral itself is made up of the skeletons of tiny, flowerlike water animals called polyps, held together by a limestone substance produced by a type of algae. Hundreds of species of polyps form coral in a beautiful range of colors and shapes. The reef also supports many larger water animals, including as many as 2,000 species of fish.
 

Global Warming

Global warming is the increase in the earth's temperature caused by the buildup of greenhouse gases (carbon dioxide, nitrogen, and methane) in the atmosphere. Greenhouse gases prevent infrared radiation from escaping into space, and this greenhouse effect maintains the earth's warm temperature. Increasing levels of greenhouse gases, resulting from industry and the burning of fossil fuels, may result in rising global temperatures, causing coastal flooding and major climatic changes. According to the British Meteorological Office, 1995 was the warmest year on record and global temperatures continued to rise. A United Nations panel of scientists has predicted that if greenhouse gas emissions are not reduced, the average global temperature could rise by 1° to 3.5° C (1.8° to 6.3° F) by the year 2100.
 

What's Happening?

Coral reefs are threatened by global warming. They can only live in waters between 18 C and 30 C. Therefore, with the increase in temperature of the surrounding water, there has been an unprecedented increase in the number of coral bleaching events during the past 2 decades (which have had some of the warmest years in history). When ocean temperatures get too high, coral polyps lose the symbiotic algae inside them, causing them to turn white, or "bleach," and eventually die.

In particular, Australia has been slow to cut back on greenhouse gas emissions.  This may explain why in 1998, almost 90% of the Great Barrier Reef was affected by coral bleaching.

Global warming trends may also lead to more extreme and unpredictable weather. An increase in tropical storms could do extensive physical damage to coral reef ecosystems. Rising sea levels may become a serious threat to coral reefs and to small island nations based on coral reef atolls.
 

Coral Bleaching

In March and April of 1998, approximately 30% of the barrier reef was destroyed due to coral bleaching. Coral bleaching is the whitening of coral colonies due to the loss of symbiotic zooxanthellae from the tissues of polyps. This loss exposes the white calcium carbonate skeletons of the coral colony. According to Dr. Ove-Hoegh Guldberg, coral bleaching occurs when algae in a symbiotic relationship with the coral become dysfunctional and expelled.  The algae (dinoflagellates) normally provide foods for the coral through photosynthesis.  However, when the temperature increases, the ability to perform photosynthesis is completely shut down.
 
 
 
 
 

A coral damaged by bleaching (on the right side) is dying (on the left side).
 
 

The future of reefs

The future of coral reefs is not bright. As of now, 10% of the coral reefs world wide have already been destroyed. At this rate of destruction, approximately 70% will be killed in the next 40 years.

In June of 1998, President Clinton issued the Executive Order 13089 which established the U.S. Coral Reef Task Force to protect coral reefs.
 

What can be done

The biggest way we can help prevent further destruction of coral reefs is to help curb global warming. The first step in reaching this goal is to educate people and make them aware that global warming exists and the consequences of it. Unfortunately, awareness isn't enough.  People have to do something.  The governments of many nations have met and passed bills and mandates to reduce greenhouse gas emissions. These include the Berlin Mandate and Kyoto Protocol.

The United States introduced the Clean Air Act which banned the use of chloroflorocarbons (CFCs).  Other ways to reduce greenhouse gases include alternative forms of energy such as solar or nuclear and taking public transportation or walking instead of driving which uses fossil fuels.
 

References

Jones, Cheryl. Global Warming kills Great Barrier Reef coral
http://www.usyd.edu.au/su/exterel/news/981008News/8.10.coral.html

Coral bleaching
http://www.uvi.edu/coral.reefer/bleach.htm

Coral Reef
http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=050FE000

Coral reefs in peril worldwide
http://usatoday.com/life/science/environ/lse011.htm

Coral 'stress' worsening, expert says
http://www.msnbc.com/news/287041.asp?cp1=1

Global warming
http://encarta.msn.com/find/Concise.asp?z=1&pg=2&ti=03CCE000

Greenpeace reports threat to Great Barrier Reef
http://www.wwinternational.com/pages/updatecontent/Reef.html

Protecting Coral Reefs
http://coralreef.gov/how.html

What are Some Solutions to Global Warming
http://www.geocities.com/RainForest/Andes/9520/whattodo.html

What are the Causes of Global Warming?
http://www.geocities.com/RainForest/Andes/9520/causes.html