Human Effects on Coral Reef Ecosystems Term Paper

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Human Effects on Coral Reefs

Coral reefs are one of the oldest ecosystems in the world, existing for more than 450 million years.

A coral reef is a type of biotic reef that develops in tropical waters. Coral reefs are found in all oceans of the world, generally between the Tropic of Cancer and the Tropic of Capricorn because the reef-building corals are living in this waters. A water temperature of 20 to 28°C is needed for growth of the coral reef. Massive reef structures are built over thousands of years by tiny coral polyps aided by minute algae called zooxanthellae that live in their tissues, calcifying algae, and other organisms that secrete calcium carbonate and adhesives. The process of reef formation is heavily dependent upon photosynthesis by reef-building organisms. Once formed, the complex, rock-like reef framework provides food and shelter for the multitudes of organisms that inhabit the reef.

Structural Characteristics

Coral reefs form when free-swimming coral larvae attach to the submerged edges of islands or continents. As the corals grow, reefs take on one of three major characteristic structures, fringing, barrier or atoll. Fringing reefs, the most common structure, project seaward directly from the shore to form borders along the shoreline and surrounding islands. Barrier reefs also border shorelines, but at a greater distance because they are separated from land by a lagoon of open, often deep water. If a fringing reef forms around a volcanic island that subsides completely below sea level while the coral continues to grow upward, an atoll forms. Atolls are circular or oval, with a central lagoon. Parts of the reef platform may emerge as one or more islands, and breaks in the reef provide access to the central lagoon.

3.0 Benefits to Humans

Coral reefs are some of the most diverse and valuable ecosystems on Earth, supporting 4,000 species of fish, 800 species of hard corals and hundreds of other species. Scientists estimate that there may be as many as eight million undiscovered species of organisms living in and around reefs. This biodiversity is facilitating the development of new drugs for cancer, arthritis, human bacterial infections, viruses, and other diseases.

Coral reefs are estimated to provide goods and services worth $375 billion each year. Reefs contribute to local economies through tourism. Diving tours, fishing trips, hotels, restaurants, and other businesses based near reef systems provide millions of jobs and contribute billions of dollars to the world economy. The commercial value of U.S. fisheries from coral reefs is over $100 million and, in developing countries, coral reefs contribute about one-quarter of the total fish catch.

Coral reefs are also important to the ecology. They buffer adjacent shorelines from wave action and prevent erosion, property damage and loss of life. Reefs also protect the highly productive wetlands along the coast, as well as ports and harbors and the economies they support.

4.0 Current Status

A study by the World Resources Institute reveals that nearly sixty percent of the world's coral reefs are now threatened by human activity. Coral reefs of Southeast Asia are the most threatened with more than eighty percent at risk because of coastal development and fishing. Most United States reefs are threatened. Almost all the reefs off the Florida coast are at risk from factors such as runoff of fertilizers and pollutants from farms and coastal development. Half of Hawaii's reefs are threatened, while all of Puerto Rico's reefs are at risk. And, nearly two-thirds of Caribbean reefs are in peril. Most of the reefs on the Antilles chain, including the islands of Jamaica, Barbados, Dominica and other vacation favorites, are at high risk. Reefs off Jamaica, for example, have been ravaged by over fishing and pollution.

5.0 Anthropogenic (Human) Threats

One of the greatest threats to coral reefs is human expansion and development that in increasing the amount of freshwater runoff. This runoff often carries large amounts of sediment from areas with deforestation activities, high levels of nutrients from agricultural areas or sewage treatment plant operations, and pollutants such as petroleum products or insecticides. Decreases in the amounts of light reaching corals are caused by sedimentation and pollution which in turn contributes to bleaching

Minute algae called zooxanthellae provide the coral with oxygen and food they have made from photosynthesis, but zooxanthellae can't photosynthesize in cloudy water. Because algae give the coral its color, the reef turns white, an event referred to as coral bleaching. Instances of multiple bleaching kill corals.

In addition, increases in the amounts of nutrients enhance the growth of other reef organisms such as sponges that take space away from corals on crowded reefs. Outflows from water treatment plants and large power plants also damage coral reefs. Sewage treatment facilities greatly increase the nutrient levels surrounding their outflow pipes while large power plants alter water temperatures by discharging extremely hot water into the coastal waters.

Coral reef habitats are overfished and overexploited for recreational and commercial purposes. Coral heads and brightly colored reef fishes are collected for the aquarium and jewelry trade and reef fishes are collected for food. The removal of large numbers of reef fish has caused the coral reef ecosystems to become unbalanced and allowed more competitive organisms, such as algae, which were once controlled by large fish populations, to become dominant on reefs in many regions. New fishing techniques that employ explosives and poisons are destroying fish and the coral habitat.

Deep-water trawling that drags a net along the sea bottom destroys coral as does achors dropped from fishing vessels onto reefs.

6.0 What Should Be Done?

According to experts, protection of coral reefs must include long-term environmental monitoring, integrated coastal management, effective marine sanctuaries, appropriate technologies for pollution prevention, and environmentally sensitive ways to exploit reef resources. These can only be implemented with substantial international economic and technical assistance. Local threats must be addressed by countries containing coral reefs, supplemented by international financial and technical assistance. Regional problems, such as the transport of water and air pollution across national boundaries, must be addressed through regional laws and international implementation assistance. International accords are required for global issues such as global warming, ozone depletion, and international trade in coral products.

7.0 How is the U.S. Government Helping?

The International Coral Reef Initiative (ICRI) is a partnership among nations and organizations formed in 1994 seeking to implement international conventions and agreements for the benefit of coral reefs and related ecosystems. Two years later, the U.S. Coral Reef Initiative (USCRI) was launched as a platform of U.S. support for domestic and international coral conservation efforts. The goal of the USCRI is to strengthen and fill the gaps in existing efforts to conserve coral reefs and related ecosystems in U.S. waters.

In 1998 President Clinton issued Executive Order 13089 on Coral Reef Protection "to preserve and protect the biodiversity, health, heritage, and social and economic value of U.S. coral reef ecosystems and the marine environment." The Executive Order directs all federal agencies to protect coral reef ecosystems and instructs certain agencies to develop coordinated, science-based plans to restore damaged reefs as well as mitigate current and future impacts on reefs, both in the United States and around the world.

There are many government funding projects to protect coral reefs. Of note is the Florida Keys Coral Reef Monitoring Project, a large-scale, multiple-investigator project funded by the EPA and designed to assess the status and trend of Florida's offshore reefs, patch reefs, and hard-bottom communities over a 5-year period. And, the EPA's Oceans and Coastal Protection Division is developing guidance on coral reef protection from a watershed management perspective.

8.0 How Can We All Help?

We can all help protect coral reefs. We can do so by not polluting water, recycling, avoiding the use of chemically enhanced pesticides and fertilizes and conserving water to reduce runoff and waste water. We can also be more responsible consumers by only buying marine aquarium fish collected in an ecologically sound manner, not starting live rock aquariums and not purchasing coral objects. When visiting a coral reef, we should respect all local guidelines, hire local guides trained in protecting reefs, avoid touching coral and anchoring on reefs, and make sure that sewage from the boat is correctly treated. And, we can support conservation organizations, many of which have coral reef programs, the creation and maintenance of marine parks and reserves and the passage of conservation laws.


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Fujita, Rodney M., Epstein, Mark S., Goreau, Thomas J. And Gjerde, Kristina. "A Guide to Protecting Coral Reefs." 1992. Available: (Accessed 25 Jan. 2005).

"How Old are Coral Reefs?" The Coral Reef Alliance. Available: (Accessed 24 Jan. 2005).

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