Copyright 1996 Jonathan Bird/Oceanic Research Group
All Rights Reserved
All images in this document are taken directly from the film.
Most of this planet we call Earth is covered by water -- a vast network of oceans and seas. We have given each body of water a separate name. But in reality, they are all connected -- an immense, watery habitat for a spectacular variety of plants and animals we rarely see, and therefore know little about.
The larger marine creatures -- like whales, dolphins, and sharks -- get most of the attention. But some of the tiniest animals in the sea may be the most remarkable -- and most essential for supporting marine life.
Within the world's oceans, the greatest variety of life is found on amazing living structures called coral reefs. These fragile reefs play a critical role in sustaining a thriving ocean habitat, especially in tropical oceans. They also provide many benefits to humans as well. Yet, coral reefs are built by tiny animals, each smaller than a pencil eraser.
Come along as we discover the secrets of these wondrous, life-giving coral reefs -- and learn what is threatening their continued health.
Coral reefs are spectacular to behold, lush gardens in the sea, supporting a staggering diversity of marine life in a densely packed, thriving marine metropolis. In fact, coral reefs harbor the greatest diversity of life in the oceans, and are second only to tropical rainforests in the number of species found in one area on Earth. Nearly 25% of all marine life depends upon coral reefs for their survival, yet reefs make up only a very small part of the world's oceans: far less than 1% of the vast ocean floor. Because of this, coral reefs are often called "the rainforests of the sea".
Nearly 400 million years ago, before there were any animals on land, the primitive ancestors of coral reefs formed in the seas. Today's coral reefs were built up during the last 10,000 years, as the last Ice Age ended and the glaciers receded. Coral reefs are the oldest complex natural communities or ecosystems existing on Earth. Some coral reef animals alive today are virtually unchanged from those found during the age of dinosaurs, 100 million years ago.
A dive on a coral reef is a voyage to another world. The surrealistic landscape is shaded in blue and surrounded by life...Life in a thousand forms. The coral reef is a gathering place in the ocean. It's a place which provides a variety of food and shelter in the tropical ocean, where such variety is hard to find. The entire tropical ocean depends upon the coral reef for sustenance.
The reef itself may look like a collection of rocks or boulders, but actually it's a living, growing organism -- a colony of tiny animals called coral polyps. These little polyps all work together to create huge and varied reefs, some of which are the largest structures on Earth, stretching hundreds of miles across.
Much like their relative the sea anemone, coral polyps have sticky tentacles with stingers to catch passing prey for food. At night, the polyps feast on small floating organic material called plankton, which populate the oceans. But their primary source of food is microscopic plant cells called zooxanthellae that actually live within the tissue of hard coral polyps. These plant cells also provide the coral's wide variety of colors.
Coral polyps grow in colonies, which means that each individual animal is attached to another, and then another. A colony can grow to be quite large. For example, this colony of what is known as brain coral is over six feet across! It contains many thousands of individual coral polyps all living together. A larger reef is formed by many coral colonies, often with many different kinds of coral. A reef may be hundreds of miles across, but it is still built by millions of tiny coral polyps.
A coral polyp is an invertebrate animal -- that is... an animal with no backbone. However, coral polyps do have skeletons, which they make with limestone. Thousands of these tiny skeletons combine to become the structure of a reef. Ever so slowly, over hundreds or thousands of years, the coral polyps add limestone to their skeletons in layers, and grow outward and upward, expanding the coral colonies and the reef.
The limestone is made of calcium carbonate. Calcium is extracted from the seawater by the polyps and combined with carbon, which is a by-product of their respiration, to produce this limestone. Corals can be either rock hard or soft. The combined skeletons of hard corals produce a rigid, boulder-like reef. Soft corals also have a skeleton -- actually tiny needle-like splinters called spicules, generally made out of calcium carbonate. The spicules are embedded in the colony to give it strength. But the space in between these spicules enables the colony to bend and sway with the currents.
Soft corals look like trees or bushes. There are many varieties of soft corals, including branching corals and gorgonians, like these sea whips. This brilliantly colored sea fan is another type of soft gorgonian coral. It is easy to see how soft corals could be mistaken for plants. But just like hard corals, they are a collection of coral polyps. While soft corals also grow in colonies, they do not form reefs like hard coral.
Most corals grow painstakingly slowly -- only one or two centimeters per year. As a result, it can take many years for a reef to recuperate from natural or human damage. Judging by the size of many of these slow-growing coral colonies, it is reasonable to estimate that some of them may be well over one thousand years old!
Coral reefs grow in tropical oceans where the water is shallow, clear, and relatively warm throughout the year -- averaging 70 to 80 degrees Fahrenheit. Worldwide, almost 100 countries have coral reefs along their shores. Most coral reefs are found in parts of the Pacific and Indian Oceans, off countries like Indonesia, the Phillipines, Australia, the islands of the South Pacific, and the countries of Southeast Asia. In the Western Atlantic, many coral reefs can be found from Florida to Brazil, in places like Belize, Bermuda and the Bahamas.
The largest reef in the world is the famous Great Barrier Reef in Australia, which stretches over 1,200 miles! The third longest reef in the world is found in the United States, off the southernmost tip of Florida, in the Florida Keys.
A few small varieties of corals are found in cold waters, like this North Atlantic soft coral. But generally coral cannot form reefs in cold water. Biologists believe that cold water inhibits the coral's ability to excrete the calcium carbonate necessary for reef building. Healthy coral reefs are critical to sustaining the tropical ocean ecosystem. The reefs provide vital nesting areas and hiding spots for fish and invertebrates in an ocean where these things are scarce. This, in turn, attracts predators to the area looking for food. The result is a teeming metropolis of marine life -- an interdependent web of life.
While a coral reef swarms with fish and other marine life, only a hundred yards away, there may be hardly any life or hiding places to be found.
Here, a piece of marine debris out on a sandy bottom has served as a foothold for a small colony of coral. This coral colony has in turn become a hiding spot for a school of Blue Chromis. As the cameraman approaches the school, they take refuge in their protective mini-reef, just as they would hide from a predator. As the reef grows larger, more fish and invertebrates will be attracted to it. In time, a giant new coral reef community will arise from these humble beginnings.
Healthy coral reefs are clearly very important to sustaining life in the oceans, but they are also important to those of us living on land. The fish on or around coral reefs are a major source of food and income in many countries. In poorer countries, some coastal communities are dependent upon the reefs for a subsistence diet.
Shallow reefs act as barriers against waves, protecting shores and beaches from washing away in storms, and protecting coastal communities. As with tropical rainforests, coral reefs contain a great variety of little-studied animals and plants that may be a potential source of new medicines helpful to humans. Some sponges found on Caribbean reefs may contain a substance that can help fight cancer.
Finally, healthy coral reefs are a major tourist attraction, bringing needed dollars to many local communities in reef areas. Some of these communities are totally dependent upon this income from tourism, and their economies would collapse without it.
Because coral reefs are interdependent with the other natural systems around them, such as nearby shoreline and forests, changes in these natural systems can dramatically impact a reef. Coral reefs are very sensitive to changes in their environment because of the specialized conditions required for them to thrive: clear, warm, sunlit shallow water.
Natural events, including hurricanes, disease and the rapid growth of reef predators, such as the infamous crown-of-thorn sea stars, can all cause serious damage to reefs. However, these natural perils are not as widespread or as consistently threatening to reefs as those that are human-caused.
A wide variety of human activity has damaged almost all of the world's coral reefs in recent years. Human damage also weakens the reefs' ability to recover from natural disasters. Some experts predict that unless changes are made soon, most of the world's coral reefs will be dead in just 20 to 40 years from human causes. This would be a major catastrophe for life in the world's oceans, and for the human communities dependent upon the reefs for food, income, medicine, and coastal protection.
The primary causes for reef damage can be traced directly to expanding coastal populations worldwide. The needs and byproducts of these communities are causing increasing stress on coral reefs
One of the biggest reef killers is something called sedimentation. Increasing coastal development and deforestation causes loosened soil or silt to wash into the sea, blocking out the sunlight coral need to grow. Sedimentation has been a major problem for the reefs of the Florida Keys and in other areas. When land is cleared to build airports, hotels or other developments, we often fail to think about how this might have an impact on long-established natural systems.
Many coral reefs are also suffering from overfishing, due largely to an increasing demand for fish worldwide and to newer, more efficient methods of fishing. When too many fish or shellfish are taken from a reef, this upsets an ecological balance in the food chain. Eventually, the whole interdependent ecosystem can breakdown with a catastrophic result: the reef dies.
Pollution is also contributing to the decline of coral reefs. Because coral needs clean, clear water to live and grow, it cannot tolerate much pollution. The chemicals used in pesticides, fertilizers, motor oil, and cleaning solutions can end up in the nearby ocean. These pollutants seriously weaken coral reefs and make them more susceptible to highly destructive diseases.
Another big threat to reefs worldwide are ships and boats. Carelessly thrown anchors and accidental ship groundings account for an enormous amount of damage to reefs. Even tourists who stand on coral or break off souvenirs cause serious harm.
Consumer demand for saltwater aquarium fish and coral souvenirs drives industries that are destroying reefs in many parts of the world. In some countries, deadly cyanide, which is very harmful to reefs, is used to catch fish for home aquariums. The cyanide stuns the fish, while also killing the surrounding coral polyps. Also, most coral found in souvenir shops is harvested unsustainably from living ocean reefs.
Coral reefs need to be protected, just like our rainforests, wetlands, and rivers. Because of their sensitivity to environmental conditions, coral reefs are also one of the best indicators of the health of our oceans.
For many years it was believed the world's oceans were limitless and that human activity could do no harm to such vast expanses of water. Now scientists have found that this is not the case -- and are urging that we rethink how we interact with our oceans, as well as with our global environment.
Nearly everything each of us does every day has an impact on our natural world. We might not realize it, but the choices we make about such things as the foods we eat, the clothes we buy, the vacations we take, the products we use -- all of these have an effect on our environment, and ultimately on the quality of our own lives. Learning about this impact, and what choices will best help to sustain a healthy planet, may be the most important thing we can all do to preserve the world's coral reefs and oceans.
Coral reefs are among nature's greatest spectacles, producing some of the finest examples of natural architecture in the world. They form communities of startling complexity and are essential to the health of the world's oceans and to many human communities as well.
Will the world's coral reefs survive so that future generations can experience their stunning beauty and continue to benefit from their many gifts? Scientists worldwide have recently issued both a warning about the dire state of coral reefs and a challenge to preserve them.
Their fate is now in the hands of all us alive on earth today.
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