Реферат: Marine Contamination Essay Research Paper Marine Contamination
Marine Contamination Essay, Research Paper
Marine Contamination and Pollution
According to the United Nations Joint Group of Experts on
the Scientific Aspects of Marine Pollution (GESAMP) of 1972,
marine pollution is ?the introduction by man directly or indirectly,
of substances or energy to the marine environment resulting in deleterious effects such as harm to living resources, hazards to human health; hindrance of marine activities including fishing, impairing the quality for use of sea water, and reduction of amenities?(Clark 3). Since the beginning of modern civilization, man has continuously polluted the oceans. As more and more pollution entered the Earth?s oceans and problems became evident, man has been given the obligation to prevent further damage. Sewage, marine debris, toxic chemicals, heavy metals, oil, and radioactive materials constitute six major categories of marine pollutants that mankind needs to prevent from entering the worlds oceans.
Sewage has a short lifespan, it decomposes due to microscopic organisms like bacteria and fungi. However, in the respiration process microorganisms consume oxygen, creating ?biological oxygen demand?(Johnston 56). If there is too little oxygen in the water to support the biological oxygen demand for these biodegraders, they die and so do all the plants and animals that depend on them for food. When raw sewage is dumped into an area without strong currents to disperse it, the oxygen is likely to be used up. When this happens, the only form of decomposition that can take place is anaerobic which takes a very long time. This process is called eutrophication (Clark 5). When nutrient rich sewage enters the ocean, an extreme overgrowth of toxic phytoplankton. This process causes what is known as red-tides that kill many forms of marine life.
Marine debris is another form of pollution that is a major threat to the earth?s oceans. Marine debris consists of discarded plastic, glass, and metal that does not easily decompose. Some debris such as abandoned ships and old cars that sink attract fish because they form artificial reefs. Some artificial reefs have been purposely made by humans out of sinking marine debris for the sole purpose of providing sea life with an ecosystem. The pollution problem is more centered around floating marine debris such as plastic. Because plastic floats it constitutes a threat to sea birds and mammals who either eat it or become entangled in it. Each year 30,000 northern fur seals as well as hundreds of thousands of other marine animals die due to being entangled in discarded plastic(Johnston 63). These plastics when eaten can lodge in the intestines and stomach to block the digestive tract to cause malnutrition and death. Not only does marine debris effect sea life, but humans as well. Marine debris interferes with ship navigation and litters beaches along coastal water.
Toxic chemicals are extremely hazardous to the oceans. Three of the most deadly chemicals are constantly running off land into water. These chemicals; DDT, PCBs, and dioxins belong to a family of industrial and agricultural chemicals that do not brake down easily in our environment. When these chemicals enter the ocean they are first absorbed by phytoplankton and zooplankton. These planktons are an important part of a fish?s diet, therefore; fish eat them and the toxic chemicals are stored in the fish?s fatty tissue. Because fish are low on the food chain, each time the toxic chemicals are passed on from predator to predator the concentration gets higher. High concentrations of these chemicals cause premature birth, birth defects, nerve damage, learning disabilities, and remain in the fatty tissue of marine animals.
Another major pollutant found in our oceans is heavy metals. Heavy metals are dense elements such as lead, mercury, and cadmium. Each of these elements has a different and harmful effect on sea life. Lead can make fish toxic for consumption and create more lead in the food chain. In animals, lead causes delayed development of offspring, nervous system disorders, and learning disabilities. Mercury is very toxic, even in low concentrations. It disrupts the central nervous system functions in animals. Mercury is extremely dangerous because mixed with other pollutants, the toxicity can be very deadly. Cadmium becomes toxic to sea animals by eventually replacing the calcium, thus making bones fragile and easily broken.
Oil as ocean pollution has been a major concern for decades. When an oil tanker explodes the oil that pours out into the water creates highly concentrated ?toxic pockets?(Whitham 100). Since oil is lighter than water it generally floats on top of the surface. The oil soaks up oxygen, blocks sunlight, and smothers plankton. Oil destroys the natural water resistance of sea bird feathers causing them to be unable to fly and drown. Marine animals swallow the oil causing intestinal problems and liver failure. Oil contamination in the ocean creates a long cycle of destruction, it clogs the gills of fish, taints shellfish, destroys natural corral reefs, and kills marine larva (Whitham 100).
The ocean is also polluted by radioactive materials. Once radioactive wastes enter an ocean they can not be removed or cleaned up, but are diluted into the large body of water. The plants and animals in the ocean develop a concentration of the radioactive material within them. This concentration can be harmless to some animals, but be lethal to the plant or animals predators. Animals contaminated by radiation that survive pass radionucleides in greater concentration along the food chain. Humans are the most effected by radiation, therefore; when nuclear waste is entered into the ocean humans are greatly effected due to rainfall and the food chain.(Seymour 22).
Pollution of the earth?s oceans has become a real problem. There are six major pollutants including sewage, marine debris, toxic chemicals, heavy metals, oil, and radioactive materials. These pollutants need to be regulated and prevented from entering the oceans. As population and consumer societies grow, pollution will become even a greater problem. The effects of each of the six major pollutants is evident, therefore; mankind needs to take preventative steps to save our ?Mother Ocean?.
Clark, R.B. Marine Pollution. Second Edition. Clarendon Press. Oxford, New York. 1989.
Johnston, R. Marine Pollution. Academic Press. New York, NY. 1976.
Seymour, Allyn H. Radioactivity in the Marine Environment. National Academy of Sciences. Washington D.C. 1971.
Whitham, B.T., A.B. Harvey, D.F. Duckworth et al. Marine Pollution by Oil. Institute of Petroleum analysis committee. Great Britian. 1974.