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Coral Reef Diseases
Coral is a simple animal that has lived in one form or another for over 500 million years (Davidson, 42). Usually when you think of coral you typically think of the order Scleractinia which are the stony “hard” corals that build most of the current reefs. Coral reefs are amazing ecosystems that help support life in many ways. They provide homes, protection, and food for many fish as well as food for humans. They attract tourists and researchers which offer employment and bring in money for many locals. They also provide many pharmaceutical uses for lifesaving human medicine. Coral reefs also help protect the shoreline of many coasts and pristine islands.
A significant sign of disease is in coral bleaching. Bleaching is when corals release their symbiotic algae called zooanthellae, typically Symbiodinium microadriaticum zooanthellae in Caribbean scleractinian corals, due to environmental stresses (Eshbaugh, 83). Some of the stresses that are thought to cause bleaching are: increased sunlight (UV rays), excess water from large storms that flood the reef, sediments covering the reef, sea surface temperature or salinity change, as well as exposure to chemicals and diseases. Coral is typically a tan, green, or blue color due to the zooanthellae that lives within the coral tissue. However, once bleaching occurs the coral tissue becomes a white color, giving it a bleached look. Coral bleaching changes the color of the tissue that is covering the skeleton, but it does not kill the tissue right away. A coral can be partly bleached, have patterns of bleaching, or be completed bleached. Either way, a coral can recover if the correct conditions for zooanthellae return. Although, the Australian Institute of Marine Science has found that if a coral has more fluorescent pigments in it the coral can survive and recover bleaching more easily. Also, the longer coral stays bleached the less likely it is to recover, thus, it becomes more susceptible to disease and even death.
Recently, disease and coral bleaching has been quickly invading many coral reefs worldwide. There has been disease as well as bleaching found in some of the most pristine areas in the Great Barrier Reef and the Red Sea, but both have been found especially in the Caribbean. There are “twenty – three differently named diseases and syndromes affecting corals alone in the Caribbean (Burke, 37).” No one is quite sure why there is so much disease there or the causes of them. There are many speculations and proposed threats such as coastal development, sedimentation, marine – based pollution, over fishing, rising sea temperatures, and pathogens (Burke), but there in no one sure answer. Many marine scientists are currently researching the causes of specific diseases as we speak. Of the many diseases in the Caribbean area 2/3 of the diseases are either Black Band Disease, White Band Disease, or White Plague (Burke, 37).
Black Band Disease (BBD) usually effects star and brain corals. This disease’s distinctive black band or mat gives it its name. Its black mat consist of cyanobacterium, sulfur – oxidizing and sulfate – reducing bacteria, heterotrophic bacteria, as well as several other microorganisms. These organisms work together in order to devour the live coral tissue leaving behind the bare calcium carbonate skeleton. Corals infected with Black Band Disease can continue to live until the black mat has traveled across and “eaten” the entire coral or the disease has disappeared from the coral. Healthy corals are infected with Black Band Disease when they come into contact with an infected coral, although, they are most likely to get BBD if the coral is injured or under a lot of environmental stress. The rate the black mat travels across the coral can vary, but it has been recorded to move up to a few millimeters per day, “consuming” volleyball size coral in a few months (http://Ourworld.compuserve.com). BBD has been sited especially in the Caribbean, the Indo – Pacific, and the Red Sea. This disease is high in phosphates and in effort to prevent the disease from occurring so much the Reef Relief organization had a ban placed on some soaps and detergents that are high in phosphates in the Florida Keys area (www.reefrelief.org).
The other two major diseases of coral reefs in the Caribbean area are White Band Disease and White Plague, both identified in 1977, which are also placed in the White Syndrome category. White Syndrome is a series of coral diseases that are similar to each other, host white pathologies, and are difficult to differentiate (http://Ourworld.compuserve.com). White Syndrome diseases have been found worldwide including the Great Barrier Reef. “In 1999 only seven reefs were infected with White Syndrome; in 2002 33 reefs were affected out of the 48 studied by the AIMS long – term monitoring team (in the Great Barrier Reef) (www.aims.gov.au).” White Band Disease was named for having a distinct white band or line that starts normally at the base of the branch of coral. It is typically found in Elkhorn coral and Staghorn coral where tissue peels off the skeleton at a consistent rate until it reaches the tip of the branch (http://Ourworld.compuserve.com). There are two types of White Band Disease: Type I and Type II. White Band Disease Type I is slow acting and only effects branching (Acroporids) coral species. White Band Disease Type II is a fast acting disease where a “bleaching edge precedes the necrotic (dead) edge by up to nine centimeters per day, allowing for the necrotic edge to catch up (www.accessexcellence.org).” Thus, making it difficult to differentiate White Band Disease Type I from White Band Disease Type II. The specific cause of both types of White Band Disease is unknown, but in White Band Disease Type I a rod shaped gram – negative bacteria was found in the coral tissues. In Type II the genus of Vibrio bacteria was found on the surface of the coral tissues. Also, White Band Disease Type I is found in the Caribbean, Philippines, the Great Barrier Reef, and the Red Sea while White Band Disease Type II has only been found in the Bahamas. The other White Syndrome disease is known as White Plague and it has typically affected many non-acroporid (non-branching) corals. It causes the coral tissue to disappear at a rate of one or more centimeters a day. It too, has two different types: Type I and Type II. Both are fast acting, although, Type II is the fastest. It has been known to “consume” one or more centimeters a day. White Plague Type I is found worldwide while White Plague Type II is found in the Florida Keys (http://Ourworld.compuserve.com).
In 1996, another rapid disease of Elkhorn Coral was found. It is called White Pox. Elkhorn Coral can only be found in the western Atlantic and Caribbean and this disease has already destroyed 50-80% of it (www.reefrelief.org). This disease can be detected by seeing unevenly shaped blotches of bare white skeleton. Some of the white blotches have been seen with filamentous algae growing within it. The specific rate of coral deterioration is unknown but seems to be fairly rapid. Also the cause of this disease is unknown and currently undergoing more research (http://Ourworld.compuserve.com).
Humans must help protect these wonders of nature. There is research currently being done to learn more about these coral diseases and others as well as their causes. It is said that there is no way to describe a coral reef and its ecology on paper. Rather when you are “confronted with the reef, awe is the most appropriate response (Davidson).” Without coral reefs our coastlines would not be protected, we would not have as much food, and economic profit of tourism would suffer. Some things that you can do either individually, as a group, or association is to record when and where you locate a prospective coral disease (longitude and latitude). Note your observations and your educated guess of which disease it may be, take photos of the observations. After which send the information to The Coral Health and Monitoring List Serve which is sponsored by the National Oceanic and Atmospheric Administration (NOAA) (http://Ourworld.compuserve.com). Some things that you can do everyday in your hometown is to raise awareness about the issues of coral diseases. Many people do not know that our coral reefs are being threatened with many diseases that could potential destroy all coral someday. You can start an organization that helps educate your local travelers on how to follow specific steps so that when they are snorkeling or S.C.U.B.A diving coral reefs do not become damaged, especially when visiting areas such as the Caribbean. Also, you can alert your local government officers about needing more protection and research on coral diseases. They will have a larger voice than yours when voting occurs on new policies regarding the environment.
Coral reefs are very important to the world as we know it, but they are quickly being threatened with disease. If we, as a human race, to do not act soon to help save the coral reefs they will not be here in the future. Our children will not be able to see the fascinating communities they provide marine animals and uses of the coral. If they are gone it will in turn affect the entire food chain. As Rachel Carson says, “… we in this generation must come to terms with nature, and I think we’re challenged as mankind has never been challenged to prove our maturity and our mastery, not of nature, but of ourselves.” Our generation must start to help find the causes of coral diseases and ways to prevent them so that other generations will be able to enjoy the beauty and uses of them, just as we do.
Burke, Lauretta and Jonathan Maidens. Reefs at Risk in the Caribbean.
Washington D.C.:World Resources Institute, 2004.
Coral Stress and Disease. 1997. 22 May 2005.
Davidson, Osha Gray. The Enchanted Braid. New York: John Wiley & Sons, Inc,
Eshbaugh, W. Hardy. Proceedings of the 4th Symposium on the Natural History of the
Bahamas. San Salvador: Bahamian Field Station, 1992.
Jones, Alick and Nancy Sefton. Marine Life of the Caribbean. Caribbean: MacMillan,
Links to Specific Diseases. 1998. 22 May 2005.
Paige, Cathie. Coral Diseases on the Great Barrier Reef. 2003. 22 May 2005.
Smith, Garriet W. The Decline of the Coral Reef—Coral Bleaching and Diseases with
Dr. Garriet W. Smith. 22 May 2005.
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