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Marine Dead Zones

The number of “dead zones” in oceans around the world grew by more than a third over the past two years, now reaching about 200 and threatening to grow larger still if sewage, fertilizer and animal waste continue to pour into the world’s waterways.

Dead zones are created when pollution, chiefly excess nitrogen and phosphorous, spurs large algae blooms. The blooms die and sink to the bottom of the ocean, where they are eaten by bacteria. This in turn uses up oxygen and the lack of oxygen in the water kills off fish, oysters, sea grass beds and other marine life, creating the so-called dead zone.

Reducing the amount of marine pollution would go a long way toward restoring the health of the world’s oceans. In many developing countries, more than 80 percent of sewage entering coastal zones is raw and untreated. But developed countries also contribute to the problem. Canada, for example, has no national standards for treating sewage and many cities in this country dump billions of litres of untreated waste into rivers or even directly into the Pacific Ocean.

Other pollutants include plastic debris, which doesn’t biodegrade, it only breaks into smaller pieces which can be carried hundreds of thousands of miles. Microscopic pieces of plastic have been found in even the remotest parts of the globe, and inside plankton, which is at the bottom of the marine food chain.

In addition to reducing pollution, increasing natural filter systems such as marshes, mangroves and coastal wetlands would help reduce the world’s marine “dead zones,” researchers say. Governments can help by increasing sewage treatment, decreasing pollution and conserving and rehabilitating natural filtration systems.

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To read more about this and other environmental health issues, go to: www.environmentalhealthnews.org, www.ourstolenfuture.org, or www.healthandenvironment.org