Coral reef formation is a long and slow process and there are a variety of different factors that corals require in order to survive.
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Sunlight: Corals need to grow in shallow water where sunlight is able to penetrate and reach them. Corals depend on a species of algae called zooxanthellae that grows inside them. The zooxanthellae transfer some food energy directly to the coral’s polyps. If waters are too deep or too murky, the zooxanthellae will not get enough light to photosynthesize. Thus sunlight is very important if corals are to flourish. ‘Corals rarely develop deeper than 50 metres’ (http://library.thinkquest.org/25713/classification.html).
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Clear water: Corals need clear water to survive and don't thrive well when the water is opaque. Sediment and plankton can cloud the water which decreases the amount of sunlight that reaches the zooxanthellae.
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Warm temperature: Reef corals require warm water conditions to survive. Corals generally live in water temperatures ranging from 25° C and 29° Celsius (http://library.thinkquest.org/25713/classification.html).
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Clean water: Corals are sensitive to sediment and . Sediments can settle on coral, blocking out sunlight and smothering coral polyps. Pollution increases nutrient levels in the water, harming corals. When there are too many nutrients in the water, the ecological balance of the coral community is altered.
Because of the specific needs of the coral reef they only form in particular areas of the world. Mainly limited to tropical, equatorial regions (refer figure 1.2).
Due to their complex requirements, coral reefs are very easily damaged. They can be destroyed by natural occurrences such as hurricanes and cyclones, or climatic changes such as El Niño or by artificial means brought about by human activity.
Coral reefs are being rapidly destroyed worldwide, scientists estimate that twenty five percent of the world’s reefs are already dead (http://edition.cnn.com/2000/ASIANOW/southeast/10/23/indonesia.coralreefs.ap/), and if that trend is to continue, coral reefs will become extinct within the next thirty to fifty years.
Because of the sensitivity to even the slightest change in local conditions, coral reefs are often the first ecosystems affected by man’s alteration of the environment (Project Aware 2000). Some of the general factors influencing the declining numbers of coral reefs are:
- Land clearance of vegetation and mangroves
- Coastal development
- Pollution
- Explosives
- Tourism.
- Global warming
There are two main categories in terms of threats to coral reefs- human and natural causes. Natural causes include changes in sea level, through El Niño or natural disasters. A drop in sea level exposes coral; a rise in sea level decreases the amount of sunlight reaching the reefs and can cause coral bleaching. Coral bleaching occurs when coral expels its symbiotic zooxanthellae. As a result, the coral looses its coloration. Without zooxanthellae, the coral polyps have little energy available for growth or reproduction. Furthermore coral diseases and natural diseases can wipe out entire strands of reef.
Human threats are varied and include ocean pollution which poisons coral polyps. Pollution takes on many forms including oil slicks, pesticides, heavy metals and garbage. Fertiliser runoff and untreated sewage introduce added nutrients to coastal ecosystems. These elevated nutrient levels promote algae growth, this can overwhelm and smother the polyps. Deforestation for agricultural or constructional use causes soil erosion and if there is a monsoon or heavy rainfall then this sediment travels to rivers and into the sea, where the coral is. The sediment can pollute the water by blocking the sunlight out and so the coral cannot breathe, or in the worst cases it can smother the coral completely, killing off sometimes the whole organism, not just a little piece. This would have a devastating impact on the diversity because a complete habitat would be lost – 22% of global reef area is affected by pollution like this.
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Cyanide Poisoning: The fisherman squirts the cyanide in and around the reefs to get to the fish and temporarily paralyse them. However, the cyanide poison floats around and kills the smaller reef fish as well as the small coral animals, and thus the coral reefs die.
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Trawling: Trawling is a method of fishing using a chain, and a big net which is dragged along the ocean floor, pulling up everything in its path, leaving the once vibrant reef ecosystem looking like somewhat of an underwater desert.
Further to these problems overfishing has a substantial effect on coral reefs and the marine ecosystem. Fishing with dynamite, cyanide or bleach has killed coral reefs in the Indo-Pacific region. Between 1986 and 1991, half of the coral reefs in the Philippines have been demolished by these and other destructive fishing methods. Since the 1960's, thousands of fishermen in Asia and Indonesia have been using dynamite fishing to collect live fish for money. It is a quick and easy way to catch fish because once the dynamite explodes, the fish nearby are stunned and float to the top where they can be caught. However, the dynamite severely damages the coral reefs and affects the biodiversity because, as mentioned earlier, the community is symbiotic and so if parts of the reef are killed, all the algae and polyp will die.
Over fishing in places like the Philippines and Indonesia has caused the disappearance of many types of fish from entire areas. With out these predators in the area, ‘pests’ like the sea urchin increase in population. Sea urchins kill live coral as they feed on algae, so eventually, algae growth overtakes the coral and can suffocate it..
Also international seashell and aquarium trades have put strain on coral reefs and reef inhabitants. Excessive collecting decimates reef species and upsets the equilibrium of the reef ecosystems. In 1990, the world consumption of corals for the souvenir trade was estimated at 2,200 tons a year. Lastly careless recreationists damage reefs. Divers and snorklers that stand on, sit on, or handle corals can injure the delicate polyps or large ships ehihc anchor on coral reefs.
How can further damage be prevented?
There are numerous ways in which corals can be protected. Coral reefs should be preserved, the establishment of marine sanctuaries or preserves may help ensure the availability of this ecosystem in years to come. An example of this is The Great Barrier Reef Marine Park which was established in 1975.
Sustainable development allows the reef to stay alive and also make the best use from it economically. Here are examples of sustainable development
1. Development to take place further away from shoreline to prevent deforestation, sedimentation runoff and preserve mangroves.
2. Heavy fines for removing coral from the sea.
3. Environmental Legislation.
4. Adequate sewage systems that pump well away from coral reefs.
5. Limit water sports to certain areas.
6. Educate tourists better about the reef.
In the case that something must be built on an area containing a coral reef coral Transplantation can always be implemented. Coral transplantation is the movement of pieces of the coral reef to another area that needs the additional colonies. An example of this is in Barbados where coral was moved from a deep water harbour to a Marine park (see figure below).
Another way of restoring or creating new reef is through the reef ball project. Reef Balls are specially created and treated concrete mounds, which mimic the appearance of a real coral reef. However, unlike the natural coral reefs, they are resistant to disease and many human related activities which affect the natural coral reefs. They are expected to last about 500 years.
Reef balls are supposed to attract marine life as usually coral reefs do, and function as real coral reefs. Some coral polyps even start to form reefs on the reef balls themselves, and thus soon, a real coral reef is seen at that spot.
Case study: Palau
The archipelago islands of Palau consist of unique terrestrial and marine ecosystems which have a delicate interdependence and support a diverse species of biotic organisms. Palau’s tropical maritime climate is a result of its location in the Western Pacific Ocean and its proximity to the equator. This provides the precise conditions for coral reefs to develop. Palau’s Marine environment is dominated by Coral Reef which exists due to the relatively nutrient depleted waters. In order for Palau’s fragile ecosystem to survive at a sustainable rate management strategies need to be imposed to avoid exploitation. But before management strategies can be imposed a careful understanding of the environment is needed. This way Palau can be effectively managed in a sustainable manner with minimal negative impacts.
Modern technology has had a negative impact on what was the Palauan’s subsistent lifestyle. Palauans had achieved a subsistent lifestyle at which an ecological dimension was reached at a sustainable rate. Technology brought the introduction of fishing nets and boats which led to commercial fishing. This allowed exploitation of the marine environment leading to over fishing. If the Marine ecosystem is given insufficient time to regenerate then the species will never recover to their original diversity. This will result in the extinction of many species of fish which in term will disrupt the complex interactions of the food web. As species diversity decreases in the ecosystem the vulnerability of the ecosystem increases. By decreasing the amount of species diversity in the ecosystem it in term reduces the resilience of the ecosystem to cope with stress. To minimize this, commercial fishing will have to be dealt with at Local, Regional and Global scales. At a Local and Regional scale Management strategies are needed to allow the ecosystems to sustain themselves and to avoid depletion. If management strategies are not emplaced correctly (at the varying scales) Palau’s marine ecosystem will decrease dramatically.
Palau’s economy consists primarily of tourism due to its intrinsic values which consequently has had a very damaging effect on Palau’s ecosystems. Due to technology which brought communication, more people learnt about Palau’s existence. Access to Palau was increased as airlines became cheaper and more readily available, leading to increased tourism which transformed the island of Palau. Tourism brought a significant rise in population which meant that infrastructure had to be built to cope with this increase. Roads also had to be built for easy access for tourism.
Due to Tourism an Increase in Inputs was needed because of the rise in population which meant over fishing and the need of inputs from exterior sources. This causes a major strain on resources and is causing the biodiversity of marine species to decrease at a growing rate. If this continues and effective management is not achieved at a local and global scale then over 10% of fish species may not exist in years to come. This is plainly due to depletion of resources at an unsustainable rate giving the ecosystem no time to replenish itself. By gaining food from other sources it affects the world at a Global scale as over fishing can result in other areas.
Due to greenhouse gases global warming has become an increasing problem in Palau. Global warming leads to coral bleaching destroying this unique attraction and habitat. Changes in the ocean currents may also occur due to Global warming. Changes to the ocean currents mean that the ocean may rise at a rate which the coral cannot keep up with, destroying the marine ecosystem of Palau. Algae are also affected as the algae balance is modified. By modifying the algae balance it affects the organisms surviving on the algae as a resource. If global warming continues to occur it could mean the destruction of the coral. This would cause a loss of a tourist attraction which would in term affect Palau’s economic activity. It would also mean the loss of an ecosystem which leads to the loss of many organisms that survived in it, and also food resources. Management needs to occur to try and reduce the rate at which global warming is affecting the world. Management strategies (at all scales) should be in place to try and decrease the rate at which global warming is occurring.
As all islands of Palau are different, individual management strategies need to be enforced to suit each need. If management strategies aren’t used at a variety of scales it will result in the destruction of fragile ecosystems all over the world.
Conclusion
Coral reefs are ecologically and economically one of the most important ecosystems in the world. They provide millions of jobs both directly and indirectly and are home to millions of species of plants and animals.
Urbanisation and tourism is a big part of the problem of the diminishing coral reef population worldwide and thus many of the problems concerning coral reefs are human induced. Activities such as construction on shorelines, pollution, deforestation and aquaculture are all damaging the fragile coral reef ecosystem.
The coral reefs are vital in attracting tourists to coastal nations. Many tourists enjoy the beauty of coral reefs and if this fragile resource were to be gone from our seas not only would the environment severely suffer but also the tourism industry.
There are quite a few steps in place to curb the decline and the destruction of the Coral reefs worldwide; in order to keep both the coral alive and a flourishing tourism sector, there needs to be consistent management of the fragile ecosystem in order to preserve this beautiful and vital resource for generation to come.
Bibliography
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Montgomery, James, 06, Figure 1.0, , accessed 5/8/07
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Figure 1.1, , accessed 5/8/07
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King, Michael, 2004, ,.Worldwide distribution of coral reefs, , accessed 5/8/07