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Tuesday, July 29, 2008

Threats to Coral Reefs

Corals and coral reefs are extremely sensitive. Slight changes in the reef environment may have detrimental effects on the health of entire coral colonies. These changes may be due to a variety of factors, but they generally fall within two categories: natural disturbances and anthropogenic disturbances. Although natural disturbances may cause severe changes in coral communities, anthropogenic disturbances have been a part of the vast majority of decreases in coral cover and the general colony health when coral reefs and humans occur together.

One of the greatest threats to coral reefs is human expansion and development. As human expansion and development continue to alter the landscape, the amount of freshwater runoff increases. This terriginous runoff may carry large amounts of sediment from land-clearing areas at times, high levels of nutrients from agricultural areas or septic systems, as well as many pollutants such as petroleum products or insecticides. Whether it is direct sedimentation onto the reef or an increase in the turbidity of the water due to eutrophication, it still decreases in the amounts of light able to reach the corals which may cause bleaching. In addition, this will increase the amounts of nutrients that enhance the growth of other reef organisms such as sponges which may outcompete the corals for space on very crowded reefs.

In addition to runoff, outflows from water treatment plants and large power plants are mainly the cause of the severe damage to coral reefs. Sewage treatment facilities greatly increase the nutrient levels which surround their outflow pipes while large power plants alter water temperatures by discharging extremely hot water into the coastal waters. And with all these factors, the basis of the continuing of the degradation of coral reefs is increasingthe size of the human population.

As the human population increases, so does the harvest of resources from the sea. Due to overfishing, the population of fish that live among the reefs have been greatly decreased in some areas of the world. The removal of large numbers of reef fish has made the ecosystems of the coral reef to become unbalanced, allowing more competitive organisms, such as algae, which were once controlled by large fish populations, to dominate the corals and fish on reefs in many regions.


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