HomeEcosystemThe Coral Reef Ecosystem

The Coral Reef Ecosystem

What is Coral?

Corals are composed of thin plates, or layers, of calcium carbonate, secreted over time by hundreds of soft-bodied animals called coral polyps. Polyps range in size from a pinhead to a foot in length. Each polyp lives in a symbiotic relationship with a host zooxanthellae that give the coral its color. Zooxanthellae take in carbon dioxide, process it through photosynthesis, and give off oxygen and other essential nutrients that are then used by the host polyp. As in all photosynthesizing organisms, this means that corals must be exposed to a sufficient amount of sunlight. This confines most corals to shallow waters that are clean and clear.

There are two kinds of corals: hard and soft. Hard corals (Scleractinia), such as a brain, star, staghorn, elkhorn and pillar corals have rigid exoskeletons, or corallites, that protect their soft, delicate bodies. Soft corals (Gorgonians), such as sea fans, sea whips, and sea rods, sway with the currents and lack an exoskeleton.

Coral Characteristics

One fascinating feature of shallow water, reef-building corals, is their mutualistic relationship with photosynthetic algae called zooxanthellae, which live in their tissues. The coral provides the algae with a protected environment and the compounds they need for photosynthesis. In return, the algae produce oxygen and help the coral to remove wastes. Deep-sea corals occur in much deeper or colder oceanic waters and lack zooxanthellae. Unlike their shallow-water relatives, which rely heavily on photosynthesis to produce food, deep sea corals take in plankton and organic matter for much of their energy needs.

What is a Coral Reef?

Coral reefs are one of the most biologically diverse ecosystems on earth, rivaled only by tropical rain forests. They are made up not only of hard and soft corals, but also sponges, crustaceans, mollusks, fish, sea turtles, sharks, dolphins and much more. Competition for resources such as food, space, and sunlight are some of the primary factors in determining the abundances and diversity of organisms on a reef. Each component of a coral reef is dependent upon and interconnected with countless other plants, animals, and microorganisms. This means that fluctuations in the abundance of one species can drastically alter both the diversity and abundances of others. While natural causes such as hurricanes and other large storm events can be the stimulus for such alterations, it is more commonly anthropological forces that affect these types of shifts in the ecosystem.

Coral Reef Ecosystem

For example, overfishing of herbivorous fish often results in increased growth of algae and seagrasses. This results in an increase in other herbivorous marine life, such as sea urchins. Over time all ecosystems will naturally establish these types of balances between predators and prey and organisms in competition for similar resources. The question is how long those balances take to develop and what other reef relationships they affect.

What is the Coral Reef Ecosystem?

The coral reef ecosystems are located around a living coral reef. The ecosystem identifies specific life forms found in the coral reef environment.

The life forms that live in the coral reef have adapted to life in a saltwater environment. The coral topography involves the reef from the deepest depths of the living coral to the islands of coral sand that is formed around reefs.

The Benefits to the Ecosystem

People receive many benefits from coral reefs. These ecosystems protect coastlines from storms and erosion; provide jobs for local communities; offer opportunities for recreation; and are a source of food and new medicines. Over half a billion people depend on reefs for food, income, and protection. Fishing, diving, and snorkeling on and near reefs add hundreds of millions of dollars to local businesses. The net economic value of the world’s coral reefs is estimated to be nearly 29.8 billion U.S. dollars per year. These ecosystems are also of great cultural importance to indigenous people in many regions of the world.

Threats to the Ecosystems

Unfortunately, coral reef ecosystems are severely threatened. Scientists estimate that the world has lost 19% of its coral reefs with an additional 35% under the threat of being lost over the next 20-40 years. Some risks are natural, such as diseases, predators, and storms. Other threats are caused by people, including pollution, sedimentation, unsustainable fishing practices, and climate change which is raising ocean temperatures and causing ocean acidification. Many of these threats can stress corals, leading to coral bleaching and possible death, while others cause physical damage to this delicate ecosystem.

The Lifeforms

Coral reef ecosystems may have similar conditions as other aquatic ecosystems underlying criteria for classification, but their life forms can exist in the symbiotic relationships needed between the ecosystem to sustain life. In all the warm oceans of the world, the coral reef offers a diverse choice of issues for life forms and plant life to deal with.

In studies of the ecosystem, the predatory nature of some forms of life will mark the food chain of the particular area. Whales and dolphins exist. In this specific ecosystem, the food chain begins with the largest predatory mammals and fish and will continue down through the strata of life forms to the smallest poly and coral life. They make the top of the food chain with fish such as sharks and large predators like turtles and stingrays.

Without the tides, the currents and the sandbars or rock reefs the plants could not exist. Without the movement of schools of fish, jellyfish, rays, eels, and turtles, the levels of life would not remain in balance. The food chain consists of smaller fish and crustaceans. It is the way that these creatures exist among the plant life and coral formations that make up the unique relationships in the coral reef. Without plant life or plankton, the larger species could not exist.

The Impact of Human Activity On The Coral Reef

The impact of human activity may not at first be discernable, but a study would give an idea of how man has changed the balance of life in any aquatic ecosystem. When looking at the ecosystem, it is essential to understand the changes that have taken place over the last hundred years. Not only through the act of fishing, does human activity impact on the coral reef, but activities such as fertilization of crops can affect the delicate balance in the marine environment. Toxins washing into the tidal zones, plastics floating through an aquatic ecosystem, long lines, waste material and oil spills can damage a fragile ecosystem.

Taking care of the reef will mean the survival of thousands of individual species. No coral reef system can exist without being impacted by what happens in other parts of the globe. This is vital to the health of all life forms that live within it.


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