Coral reefs are the rainforests of the sea: diverse, vibrant, beautiful, and desperately endangered.

Anthropogenic fluxes are causing the destruction of these systems.

1. Defining and Understanding Coral and the Coral Reef
2. The Destruction of Coral Reefs
3. The Negative Effects of this Destruction

4. Sources

This organism is one species of coral polyp.


1. Defining and Understanding Coral and the Coral Reef

    In order to understand exactly why human actions have had such a dramatic effect on coral reefs, it is necessary to understand what coral and coral reefs are and to know a little bit about how reefs form. This knowledge will also help you to understand why coral reefs are so valuable to humans and why their destruction should be prevented.

     Many people do not understand the difference between “coral” and a “coral reef”. Though these two terms are intrinsically related, they are not to be interchangeably.

What we tend to refer to as "Coral” is actually the skeletal remains secreted by small marine polyps. Coral is actually a tiny animal that looks like an upside-down jellyfish; It is in the same family as a jellyfish, classified as a benthic cnidarian. There are hundreds of species of corals, divided into two general categories, soft corals and hard corals. Soft Corals are treelike and flexible. Hard corals are the reef building corals we are most familiar with. Unless otherwise specified, “coral” will refer to “hard corals”.

Corals form the Structure of a Coral Reef:

Baby coral polyps build shells made by combining Carbon Dioxide (CO2) and Calcium (Ca) to form Calcium Carbonate (also known as Limestone). When polyps die, new ones land and form right on top of them. The physical structure of each coral reef is formed by millions of coral polyp shells. These colonies form the environment for all the organisms that thrive in coral reefs. Coral, essentially, is the building block which enables all other reef life to survive.

Purple Sea Squirts are one example of
rare and exotic life found  in the reef habitat.

Life in a Coral Reef:

The term coral reef refers to a system composed not only of corals and the physical structure their remains provide, but also of thousands and thousands of living organisms: fish, marine plants, sponges, mollusks, algae, etc

A magnified image of Zooxanthellae,
the algae necessary to coral survival


Zooxanthellae is an algae essential to the survival of coral reefs. They live inside coral and share a symbiotic relationship with them. Zooxanthellae provide oxygen and other nutrients to the coral polyps and the polyps give the algae the carbon dioxide they need to survive. Zooxanthellae also give coral its beautiful color. Without Zooxanthellae, Coral have clear bodies and white skeletons.


The Formation of the Reef:

Coral Reefs require specific conditions to thrive. They form in shallow (depths of less than 27 meters) clear water where the sunlight can easily reach them. This is important because the zooxanthellae need sunlight to perform photosynthesis. They require a fairly narrow range of temperatures (between about 20 and 30 degrees Celsius) which is why they form in warm geographic regions. They require a salinity between 34 and 37 parts per 1000, so they don’t do well near freshwater runoffs or in conditions where the water conditions change a lot. Almost all reefs grow in shallow waters bordering land, making them very vulnerable to anthropogenic fluxes.


The Necessity of Coral to the Coral Reef:

Though coral reefs are not composed solely of coral, the survival of the organisms in the reef habitat is dependent above all on the survival of the coral formations. When the health of the coral is threatened, the existence of every other species is threatened, too. The destruction of coral is leading to the endangerment and extinction of thousands of other species.



2. The Destruction of Coral Reefs

Coral reefs are being destroyed by anthropogenic fluxes in their environment. These fluxes are caused both directly by people who have physical contact with the reefs and by all other people who contribute to earth’s pollution.

Direct Contact: Fishing

Humans destroy coral reefs directly through unfriendly fishing habits. Many coral reefs are overfished, destroying their sustainability. In other areas, practices like cyanide fishing and blast fishing destroy reefs. Cyanide fishing is a method in which divers squirt cyanide into reef crevices and onto fish, stunning them and making them easy to catch. Small organisms, especially coral polyps, are killed by the cyanide in this process. Blast fishing, in which explosives or gun shots are sent into the reefs, can completely destroy the reef structure.

Unsafe Fishing Practices result in the death of coral and other organisms that live in the reef.

Direct Contact: Tourist Economies

Tourism has caused severe damage to the reefs. Corals are often removed from their habitat to be sold as souvenirs. Also, in some coastal areas with rapidly growing populations and development, piers and docks have been built right on top of coral reefs. Careless divers often inadvertently destroy coral reefs by kicking them or dropping anchors from their boats directly onto the coral. In poorer countries, septic waste from resorts often leaks out into the ocean, killing off the fragile corals.


   However, much of the destruction of coral reefs is caused by people who have never even seen a reef. The pollution which has adversely affected the earth over the last century has had a dramatic effect on the health of the reefs.

Pollution: Global Warming and Ozone Depletion

 Global warming has translated into oceanic warming, the rising temperature of earth’s oceans. This process, combined with the depletion of earth’s ozone and subsequent increases in ultraviolet radiation, has lead to what is known as “coral bleaching”. Coral bleaching occurs when the coral polyps, stressed by changes in temperature or UV radiation, expel the zooxanthellae which are necessary for their survival. This not only “bleaches” them and causes them to lose their color, it often leads to their death.

Pollution: Increased CO2

Increases in the amounts of carbon dioxide found in water have had an adverse effect on coral. The Carbon Dioxide seems to be dissolving the coral skeletons and making them much weaker. The process has been compared to osteoporosis in humans, and is leaving the fragile coral structures weak and even more vulnerable to anthropogenic fluxes.


Pollution: Water Contamination

Oil spills, waste dumping, and other byproducts of human advances have resulted in the contamination of the oceans. When the homoeostasis of the reef area is lost, there is an overgrowth of algae. When too much algae grows on the reef, the coral cannot get enough oxygen and is the reef is effectively smothered by Nitrogen and Carbon Dioxide.
This crab makes his home in the coral reef.

3. The Negative Effects of this Destruction 

The End of Habitats with a High Density of Biodiversity:

Coral reefs are truly the rainforests of the sea. They cover only about 1% of the ocean floor, yet are home to about 25% of all marine life- approximately 35,000 to 60,000 different types of organisms. They are beautiful, lush, habitats brimming with natural resources.

The Demise of Economies Dependent on Reefs:

Many humans are dependent on Coral Reefs for their livelihood. It is estimated that reef fish and mollusks feed between thirty and forty million people each year. Also, beautiful and exotic reef fish can also be sold as pets, providing cash income to families in poverty stricken areas. Tourism provides the basis for entire economies in many regions. With responsible treatment of the reefs, it would be possible to sustain the lives of people who have close relationships with the reefs.


The Loss of Natural Coastal Protection:

Reefs form near the shores of low lying coastal lands. They are a natural barrier of protection against currents, strong waves, and storms. Without the reefs to slow the water before it reaches the shore, these areas are very vulnerable.  In one area where a reef was destroyed, it cost about $10 million per kilometer to build a protective wall along the coastline.

Killing the Hope for a Cure:

Coral reefs are probable sources of medicines to cure the diseases that currently plague the earth. Chemicals found in the reefs have been used to treat ulcers, heart disease, leukemia, and more. In one of the most famous instances, AZT, which is based on chemicals extracted from a Caribbean reef sponge, has been used to treat HIV infections. Currently, more than half of all cancer research is focused on finding cures from marine sources. Every time a reef is destroyed, the chance of relieving the pain and suffering of people all over the world is reduced.

In the background of this beautiful scene, it is possible
to see the reef which protects the shore from destruction


Shrinking a CO2 Sink:

As mentioned earlier, coral polyps use Carbon Dioxide to form their shells. This helps decrease the amount of carbon dioxide in the ocean and is one way the Earth combats pollution and works to regain homeostasis. With less coral, the ocean absorbs less Carbon Dioxide, leaving more in the atmosphere.

4. Sources


Animal Diversity Web:$narrative.html

University of Kansas

Reef Guardian International:


International Coral Reef Information Network: