Copyright © 2007 The Ontario Educational Communications Authority. All rights reserved.Canadian and World Issues CGW4U-A Lesson 13, page 7The Ocean Mess: The Tragedy of PollutionIt was once thought that the oceans were so big that anything could be poured into them and it would “dissolve” away. Ships would clean out their tanks while at sea, coastal towns would pipe untreated waste directly into the ocean, and dangerous chemicals would be put in containers and dumped into the water. This was the dilution theory. How wrong and dangerous that was.The seas are now so contaminated that a study in 2005 warned the public against eating too much salmon, as they probably contain harmful chemicals, in small amounts, that would be dangerous to human health over the long run. Imagine what these pollutants are doing to the species that live in the oceans.Surprisingly, contaminants carried in the air are responsible for a full third of ocean pollution. This pollution is emitted into the air over land and eventually deposited into the oceans through wind and rain. As you have already learned, the oceans absorb and store an enormous amount of carbon dioxide that is produced by the burning of fossil fuels in industries and automobiles. There is a major concern that too much carbon is entering the oceans and threatening species and their ecosystems. Land-based pollution that destroys the Earth’s ozone layer of protective gases is also allowing harmful ultraviolet radiation to penetrate the oceans and harm oceanic plankton. These tiny organisms are the first layer in the marine food chain. Destroy them and the food chain collapses.About 44 percent of the ocean pollution simply pours in via streams and rivers. Farmers are responsible for much of the pollution. A large amount of agricultural chemicals enters streams and rivers, and eventually the oceans. Herbicides, fungicides, and pesticides first damage the groundwater, and then flow into the drainage system to the oceans. Algae growth chokes off oxygen to other plant and animal species when it enters the oceans. Algae blooms—“red tides”—are common around many shallow seas. About 85 percent of all these
Lesson 13, page 8 Canadian and World Issues CGW4U-ACopyright © 2007 The Ontario Educational Communications Authority. All rights reserved. pollutants have a land-based source. To clean up the oceans, it is necessary to address sources of pollution on land well away from the oceans and seas.About 3.2 billion people—half the world’s population—live within 100 kilometres of a coastline. Thirteen out of fifteen of the world’s largest cities are on coastlines or on a major river that flows into the ocean. Many coastal communities have little or no environmental regulation controlling what is poured into the oceans. Huge pipes discharge industrial waste directly out to sea. Even where waste is stored, there is a high level of seepage into the surrounding groundwater. Oil refineries located around
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