Coral Reefs Final
This topic submitted by Patrick Potts (
firstname.lastname@example.org) at 10:56 PM on 6/9/05.
After 10 years of trying, Hays finally spots a "Red Eyed Tree Frog" in Costa Rica
Coral reefs are truly an incredible phenomenon. They are the biggest biologically built body known to man, and hence are visible from outer space (Wood, pg. V). Although people around the world are conscious of coral reefs existence, “the nature of the coral polyp itself and the multitudinous life of the reefs are practically unknown even to the people most interested in the sea’s marvels” (Voss, pg. 9). Essentially, people know of coral reefs—at least because of their sheer size and extensive growth throughout the world—but not really about coral reefs. People do not understand that even beyond scientific terms, coral reefs are extremely important to the world around them. In terms of economics, through living resources (such as fish) and services (such as tourism) coral reefs are valued at approximately $375 billion a year (Bryant, pg. 8). Their importance to mankind goes far beyond science and economics, and in this paper I will attempt to convey this theme. My examination of coral reefs will span the specifics of the coral polyp itself to the conservation methods used to conserve these wonderful entities.
To understand the broader picture of the coral reef, we must first understand the actual anatomy of the coral itself. There are many different species of corals, but all corals consist of small organisms called polyps. A polyp is comprised of two cell layers—the epidermis and the gastrodermis. The skeletal wall that surrounds each polyp is known as the theca (Turner, Anatomy of Corals). The polyp is in a beneficial symbiotic relationship with a form of algae termed zooxanthellae. In this relationship, the polyp feeds and protects the “zoox” from herbivorous fish, while the algae in return gives nutrients that sustain the coral polyps. It is this symbiotic relationship between the coral polyp and the zooxanthellae that is the basis of all life on coral reefs (Davidson, pgs. 15-16). The final aspect concerning the anatomy of coral that I would like to discuss involves the physical construction of coral reefs. Corals—with the help of zooxanthellae—construct a stony skeleton through the method of putting down coats of calcium carbonate or a type of limestone. It is this stony skeleton that is the physical foundation of the entire reef (Davidson, pg. 17).
There are two types of corals in terms of skeletal formation—perforate and imperforate. Perforate corals have permeable skeletons with attachments between the polyps through the skeleton. Imperforate corals have firm skeletons. Corals also have diverse growth forms. Corals can be plocoid (as in orange cup coral or golf ball coral) meandroid (as in pillar coral) cocoid, spherical shaped, or phalecoid. With all these different skeletal configurations and growth forms, it is easy to comprehend how many different types of corals there are throughout the world (Turner, Anatomy of Corals).
Coral reproduction is another interesting aspect of corals. Corals demonstrate both sexual and asexual reproduction. A general form of asexual reproduction in corals is fragmentation. Pieces of broken coral that land on suitable ground has the ability to grow and eventually construct a different colony. Fragmentation is common in branching corals like Acropora cervicornis. Mass spawning is a form of sexual reproduction in corals. In a twenty-four hour period, all the corals from a certain species will discharge their eggs and sperm at one time. Spawning is seen in species such as Montastraea, Montipora, Platygra, Favia, and Favites. The final form of reproduction I would like to mention is when coral brood their larvae. In this instance, the sperm fertilizes the egg within the coral, and then the larvae is freed into the water. Species of Acropora are known to exhibit this form of reproduction (Turner, Coral Reprocuction).
There are three major types of coral reefs studied throughout the world: fringing reefs, barrier reefs, and atolls. Fringing reefs are found close to shorelines and leave only a “narrow, shallow, lagoon between reef and land.” This particular type of reef is found in the Red Sea, along the coast of East Africa, around the Indo-Pacific Islands, and most Caribbean reefs are also in this group. Atolls are “horseshoe or ring-shaped reefs, each surrounding a subcircular lagoon.” These reefs are most frequently found in the Indian and Pacific Oceans. Barrier reefs are similar to fringing reefs because they are linked with land, but they are found at a much greater distance from the shore. This type of reef is usually far enough from land to allow ocean liners to safely pass between the two. Barrier reefs are anywhere from 300 to 1000 meters wide. The most widely known reef of this category is the Great Barrier Reef near Australia (Dubinsky, pg. 2).
Coral reefs have long been known as the “rainforests of the marine world.” Similar to rain forests, coral reefs flourish under nutrient deprived circumstances. Through an extremely effective recycling procedure, both of these bodies support plentiful communities. Both also support great levels of species diversity. With over 4,000 species of fish and 800 species of corals, it is easy to understand that coral reefs are amongst the most biologically abundant ecosystems on Earth. Some scientific estimates assert that there are as many as nine million species associated with coral reefs (Bryant, pgs. 8-9). Osha G. Davidson states, “With (coral reefs) micro-scale habitats are separated by only feet, sometimes inches.” The simple fact that habitats on coral reefs are divided by inches truly demonstrates the complexity and biodiversity of these systems (Davidson, pg. 91). Furthermore, the reef is residence for an amazing amount of species of “fishes, shrimps, worms, snails, crabs, lobsters, sea cucumbers, sea stars, urchins, anemones, sea squirts, and sea plants” (Davidson, pg. 5). Similar to rain forests, coral reefs are also home to many medicines. Coral reefs species have promise for medicinal purposes because of the vast range of chemicals they manufacture. These chemicals are being used to treat viruses, leukemia, skin cancer, and other tumors. Other than chemicals produced by coral reef species, corals have been used extensively for bone grafts. These coral reefs species offer real promise for the future in terms of medicine (Bryant, pg. 9).
Humans’ destructive behavior throughout the world has seriously damaged the coral reef network. The first aspect of humans’ harmful actions concerns coastal development and inland pollution. In many regions of the world, coral reefs are mined for construction materials. Using the sand and limestone from coral ecosystems, construction workers make cement for their buildings (Bryant, pg. 11). Davidson cites Jakarta Bay as a prime example of a mined coral reef. Since at least the mid-1800’s, the reef in Jakarta Bay has been mined for construction for the city of Jakarta (Davidson, pg. 125). In many instances, cities with little space decide to build directly on top of coral reefs. In the past, airports and other construction projects have been built on coral reef systems. Coastal development also leads to a dramatically higher rate of inland pollution affecting coral reefs. Eutrophication is one facet of this pollution. When cities release sewage into the ocean near coral reef systems, the extra nutrients lead to algal blooms. This additional algae blocks sunlight from corals and therefore inhibits coral growth. As Gilbert Voss articulates, even modern coastal Florida “hasn’t solved the problem of what to do with its sewage” (Voss, pg. 47). If we expect third world countries to properly conserve coral reefs, the richest and most progressive country in the world should at least set an example in this area. Land erosion is another characteristic of inland pollution. Sediment, pesticides, and pollution make their way to coral reefs when soil erosion occurs (Bryant, pg. 13). Zar Dubinsky articulates that coral reefs can withstand some sediment, pesticide, and pollution, but if there is an excessive degree of these substances continually over time the coral will eventually die (Dubinsky, pg. 443).
The second facet of humans’ destructive behavior involves the Greenhouse Effect. The huge amount of carbon dioxide—which allows solar energy in, but not the heat that is generated to leave—that humans have released into the atmosphere has caused global temperatures to rise, including water temperatures. When water temperatures get too high, the zooxanthellae abandons the coral polyp, known as bleaching, and the coral quickly dies. Because humans burned fossil fuels and released carbon dioxide into the air unregulated, the coral reefs have suffered immensely (Davidson, pgs. 191-192). Another side of the Greenhouse Effect harming coral reefs relates to the increased frequency and intensity of storms. The end result is “greater physical damage by storms to coral reefs” (Bryant, pg. 15).
The final feature of humans’ destructive behavior entails overexploitation and destructive fishing practices. When overfishing occurs on a reef, the delicate balance of the ecosystem is shifted. For example, when a predator is removed from the reef its prey multiplies greatly. If its pry happened to be a burrowing urchin—which eats the coral—it would increase reef attrition. If too many herbivorous fish were caught, then the algae population would explode. Therefore, the augmented amount of algae would block sunlight and cause more corals to die. Overexploitation of reef species results in harmful changes to the ecology of the reef. Destructive fishing practices fall under this category as well. When fisherman utilize bombs, cyanide, or muro-ami netting (“pounding reefs with weighted bags to scare fish out of crevices”) they don’t just get the fish they were after, but they also devastate the surrounding creatures and vegetation. These fishing practices have obvious results: death to everything in the immediate area (Bryant, pg. 12).
Because of these aforesaid reasons and some others not mentioned in this paper, coral reefs have been destroyed at an alarming pace. A study from 1993 found that 10% of the world's reefs are dead and 30% are likely to die within the next ten to twenty years. A more specific study has stated the following concerning the world's coral reefs: 36% of all reefs are threatened by overexploitation, 30% by coastal development, 22% by inland pollution and erosion, and 12% by marine pollution such as oil spills by ocean liners. A cumulative analysis of these specific threats states that 58% of all reefs are at risk (Bryant, pgs. 7-20). A more recent study from 2004 proves these dire predictions are coming true. According to this analysis, 20% of all coral reefs have effectively been ruined and do not have the possibility of recuperating. Furthermore, 24% of coral reefs are currently under immediate danger of breakdown and another 26% are under a long term threat because of humans' actions (Coral Reef webpage).
With all this distressing information pertaining to humans' harmful behavior and the percentage of coral reefs that have already been destroyed, what is being done to conserve these wonderful marine bodies? The most important thing to remember is that the problems bothering coral reefs are complex, and therefore the solutions must be. An integrated approach must be taken, "involving investigations of links among ecosystems--terrestrial, riparian [along rivers], and marine--and including both socioeconomic and ecological perspectives." Everyone--inlcuding scientists, social scientists, local and national politicians, fishermen, community groups, environmental organizations, and individual citizens near the reef--must be involved in this process (Davidson, pg. 173).
I would like to quickly examine some basic ideas on how to preserve reefs around the world. Gilbert Voss writes, "The main cause of physical damage to the reefs and adjacent areas is from user ignorance and inexperience compounded by carelessness." Thus, a good eductation program must be instituted by local or national governments. Combating ignorance is one way to help prevent future deterioration of coral reefs. Voss also presents other options including limiting access to actually closing reefs. For Voss, the action taken depends on the amount of decline of a particular reef. If the reef is in good shape and has little deterioation, maybe just limiting access will revive the reef. But if the reef is in bad shape and is only getting worse, perhaps the only option is to shut down the reef entirely (Voss, pgs. 67-68). A million different strategies could be presented, but "the ultimate success of a conservational management plan depends upon its acceptance by users and the level and nature of enforcement by managers" (Dupinsky, pg. 466).
Similar to Osha Davidson, I feel hope and despair when I think of coral reefs. Although more people than ever now know that coral reefs are facing real problems, are those people going to act or sit on the sidelines while more coral reefs die? Is it too late for anything to be done anyway? I believe it is too early to know for certain what the fate of coral reefs will be, but I believe if people act throughout the world something can be done to at the least slow future decline (Davidson, pg. 221). One thing is for certain, "the need to develop sound management policies is becoming increasingly more urgent as population growth and man's uses of reef resources continue to escalate" (Dubinsky, pg. 450).
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Tropical Ecosystems of Costa Rica
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