The importance and unfortunate distinction of coral reefs, Environmental


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The importance and unfortunate distinction of coral reefs

The importance and unfortunate distinction of coral reefs Nestled in tropical ocean waters, coral reefs provide valuable resources to both human and marine life. Coral reefs are estimated to contain one-quarter of the undersea world’s diverse species while covering less than 0.2 % of the ocean floor. However, coral reefs are in serious danger due to both natural and man-made causes (Edmonds, 1998). Population growth and development has altered the coral reef environment. Destructive fishing practices, land-based sources of pollution such as agricultural runoff, and excessive coastal development all have detrimental effects on delicate reefs. Global warming due to increased concentrations of greenhouse gases may result in sea-level rise and higher ocean temperatures, both of which have the potential to be destructive to coral reefs. In Florida, living animals whose skeletons make up the foundation of the multi-colored underwater reefs, corals are an important part of the aquatic ecosystem. Florida’s coast has the only living coral reefs in the continental United States. These ancient, slow-growing structures are now imperiled by their own enormous popularity. Boat anchors and groundings, heavy use by divers and snorkelers, and pollution all cause damage to the reefs. (Grigs, 1997). Corals are made up of tiny cup-shaped animals called polyps, which are similar to jellyfish. They begin life in tropical waters as free-floating larvae but eventually settle on the ocean bottom and form large, sedentary colonies. A single polyp may eventually become as large as a saucer or stay as small as the head of a pin. All polyps start off small and some single polyps become large. Billions of polyps working together, generation after generation, create one of nature’s most spectacular and enduring wonders: a coral reef. (Edmonds, 1998) A coral polyp is made up primarily of clear tentacles and a mouth. It feeds by waving its tentacles through the surrounding water to attract tiny wandering animals called zooplankton, which the polyp stuns with stinging cells located on its tentacles. When a polyp is feeding or defending its territory, it stretches itself out of its “cup” and spreads its tentacles like the branches of a tree. At rest, it pulls its tentacles into the cup and closes its mouth tightly (Griggs, 1998). Corals were once incorrectly classified as plants. They are animals that collect their own food instead of producing it themselves like most plants do (Griggs, 1998). According to Cousteau, the coral polyps give these brown in color algae a safe haven from predators. The algae in return, is believed to provide the polyps with a natural sunscreen and additional oxygen. The algae also provides carbon compounds to the coral, which are used to supplement its zooplankton diet. Coral reefs, for the most part require clear water, bright light, oceanic salts, and water temperatures that average approximately 70 degrees. Most polyps, rest during the day, while the algae produce energy. The polyps become active at night to gather food. Corals usually reproduce during the night and at certain times of the year. They generally spawn in response to lunar cycles. The most well known example of spawning in response to lunar cycles are the mass spawning events in the Pacific and Caribbean stony corals. During this stage, the corals produce a milky cloud of eggs and sperm. If this took place during the day, the eggs and sperm would be quickly eaten by fish and other predators. After the eggs are fertilized and they hatch into larvae, they drift with the current for several days to several weeks before settling on a hard surface. As soon as they land they begin to construct skeletons to attach themselves to the rock. At this time the larvae change from shapeless masses to polyps with tentacles and mouths. The polyp will remain in one place its entire life, growing new polyps by cloning itself. This process is called “budding.” (Griggs, 1997) During their lives, coral polyps extract calcium from the seawater and mix it with carbon dioxide to build protective limestone skeletons. These skeletons form the gradually evolving framework of the huge and colorful coral reefs. The living polyps grow on a graveyard filled with countless skeletons of other polyps. Coral reefs are built polyp by polyp, this process is usually very slow: estimates of growth range from one to sixteen feet every 1,000 years. (Griggs, 1997). The Value of coral reefs is that they are one of the most productive ecosystems on the Earth. Much of the productivity derives from the substantial concentration of marine biodiversity in coral reefs. The coral reef is the most complex, species-rich, and productive marine ecosystem (Bryant, 1993). One estimate proposes that coral reefs have about 1 million species living off of the reef. Fish and other organisms typically school along the reef, while small ones pack into the thousands of crevices. There are many reasons why coral reefs are an important part of society. The benefit from coral reef services is both immediate and long-term, making them a priority for conservation. In one case, people who are poor and are located within the coastal zones, depend directly on the reef to meet their protein needs. (Bryant, 1998). The reefs also protect the land in which they encompass. The protective services provided by reefs reduce storm damage, coastal erosion and flooding. Over time, coral reefs have enabled the formation of lagoons and calm shorelines where sea-grass beds can flourish, providing habitat for numerous species along the coast (Bryant, 1998). Some people even need coral reefs to satisfy their medical needs. About half of the potential pharmaceuticals being explored are from the oceans, many from coral reef ecosystems. Several promising drugs have already been identified, developed, and tested (Bryant, 1996). Even though coral reef systems are very useful, they are slowly deteriorating due to natural and man made causes. Due to the potential vulnerability of modern corals to high temperature, coral reefs are starting to show signs of stress from global warming (Richmond, 1998). Detecting this change will require an extensive network of monitoring sites throughout the coral reef regions of the world. This change in temperature causes coral bleaching, which is the whitening of coral colonies due to the loss of zooxanthellae from their tissues. (Griggs, 1997) This loss exposes the white calcium carbonate skeletons of the coral colony. Without zooxanthellae, the coral polyps have less energy available for growth or reproduction. (“Coral Reefs: Journal of the International Society for Reef Studies.”). Bleaching is a natural phenomenon and is not lethal unless it occurs for long periods of time. Changes in sea level are detrimental to established corals and reefs. If there is a drop in sea level the corals are exposed. This would not be healthy because corals depend on water to survive. If a rise occurs it decreases the amount of available sunlight and may inhibit growth. Added emissions of carbon dioxide into our atmosphere may be causing a gradual warming of our planet. This warming could cause the polar ice caps to melt, thereby raising sea level. (“Journal of Marine Systems.”). Four coral conditions have been identified as diseases: white band disease (WBD), and black band disease (BBD). (Richmond, 1993). These diseases are all stress related. Diseases such as BBD and WBD actually kill coral tissue, yet leaving the white coral skeleton behind. When BBD kills part of these colonies, the skeleton is available to be colonized by other coral species recruits, which is believed to be caused by a bacteria pathogen yet unknown. has much of the same effect on corals, leaving behind a white, lifeless coral skeleton. (Edmonds, 1998). WBD destroys the reef structure because the dead coral skeleton brought about by the algae is colonized by algae, invertebrates, gastropods, and sponges that work to weaken the coral skeletons making them more susceptible to breakage during storms. These diseases are highly transmittable, so healthy corals may get BBD through contact with an infected coral. (Edmonds, 1998). Besides all of the natural deteriorations of coral reefs there are many human causes. The use of cyanide to harvest live coral reef fishes is a serious threat to some of the world’s richest coral reefs. Cyanide is used by fishermen to stun and capture reef fish alive. The cyanide also kills untargeted corals and many other coral reef organisms. Cyanide fishing to collect aquarium fishes was first reported in the Philippines in the 1960’s. Since then, more than a million kilograms of cyanide has been used on coral reefs in that country (“Journal of Marine Systems.”). Recently this destructive fishing technique has spread to other countries to meet the growing demand for ornamental aquarium fishes. Coral reefs are critical to food security. Coral reefs and associated sea grass habitats provide fishery resources that are a critical source of food. Reefs contain over 4,000 species of fishes as well as crustaceans, mollusks, and other edible invertebrates. Over-fishing threatens these resources throughout the world. Reef fisheries have already been greatly diminished by over-fishing and habitat destruction. (Richmond, 1998). The commercial extraction of corals for aquarium and ornamental specimens, jewelry, and construction materials is joining the threats as cause for concern to the structure and function of coral ecosystems. Precious corals are generally extracted using destructive trawls and tangle-net dredges. Commercial extraction of corals has damaged essential reef habitats and is believed to be causing local depletions of rare species in some areas (“Coral Reefs: Journal of the International Society for Reef Studies.”). Land-based sources of marine pollution pose the greatest threats to coral reefs because of their widespread impact on water quality. Accounting for 80 % of all marine pollution, land based sources of marine pollution include coastal development, agricultural practices, industrial activities, and inland deforestation (Ricmond, 1998). Ocean pollution poisons coral polyps. Pollution takes on many forms including oil slicks, pesticides and other chemicals, heavy metals and garbage. Fertilizer runoff and untreated sewage introduce added nutrients to coastal ecosystems. These elevated nutrient levels promote algae growth. Unfortunately, high concentrations of algae or solid sewage can overwhelm and smother the polyps. Under normal conditions, herbivores fish and some invertebrates keep the algae population in check, but over-fishing has diminished populations of herbivores. Deforestation degrades more than just land habitats. When tropical forests are cut down to clear land for agriculture, pasture, or homes, topsoil washes down rivers into coastal ecosystems. Soil that settles on reefs smothers coral polyps and blocks out the sunlight needed for corals to live. (“Journal of Marine Systems.”) Tourism presents specific threats, both direct and indirect, to coral reef ecosystems, often leading to the destruction of the economic and natural resource based upon which it depends. Direct tourism threats include: damage to corals by divers, snorkelers, boat anchors and damage by cruise and recreational boat groundings. The many tourists also contribute to the polluting of the reefs. Bibliography:

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