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Report on the Health of the World's Oceans (4)

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Pollution

Unfortunately, overuse and poor management are not the only problems the oceans have to contend with. Another major problem is pollution. This pollution comes from sources on land and sea. Seventy-five percent of the pollutants in the ocean are estimated to be from the land (5). The connection to land-based pollution sources can be observed visually by 58 known "dead zones", areas where ocean life is absent, all located along coastlines (13).

Pollution carried by rivers, and agricultural runoff is a major source of pollution from the land. The increased use of fertilizers on agricultural crops, lawns and golf courses, has led to more of these fertilizers ending up in the oceans. The same effect that the fertilizers have on land plants, occur within the ocean on plants and algae. An increase in "toxic blooms" of algae, causing widespread death of marine creatures, and illness and death in humans can be linked to increased nutrients added by fertilizers and other wastes (5).

This process of increased algal growth and nutrient enrichment, is known as eutrophication, and causes a decrease in oxygen in the water (5). In the Gulf of Mexico, a 7,000 square mile area from the mouth of the Mississippi, to the Texas border, becomes so oxygen-deficient each summer that nothing can survive, creating a massive dead zone (17). The nutrient pollution is probably tied to farms throughout the Midwest. Runoff from these farms goes into the Mississippi, and ends up flowing into the Gulf (17). Each year the dead zone increases in size, and creates more damage to the Gulf waters.

Ironically, one dead zone between Denmark and Sweden, actually increased catches temporarily (17). Record catches of Norway lobster were being recorded, when oxygen levels were very low. The lobster normally burrows into the sea floor, but with the low oxygen levels, they swam up higher to locate oxygen, and made themselves susceptible to trawling (17).

Industrial pollution, and toxic wastes that leach into the groundwater flowing to the ocean, are other sources of pollution. The Calcasieu River flowing into the Gulf of Mexico carries toxic chemicals from disposal sites (15). Air pollution sweeping in from South and Southeast Asia is a primary contributor to pollution over the Indian Ocean (14). In the United States, mercury from the air is the primary source of the mercury accumulating in fish (7). About 200 tons of mercury is released into the air each year according to the U.S. Environmental Protection Agency (7). Debris from crowded beaches sweep into the oceans on a daily basis, and using oceans as disposal sites for garbage is more common than we'd like to believe.

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