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 Home >> Eco Scope >> Environment
 There are 150 'dead zones' in the world's oceans
By Hi-Tech-Editorial Division
Published on February 9, 2006, 11:03 am

It is only a few decades that humans have begun to unravel the mystery of the oceans, which cover more than 70% of the earth's surface.

Oceans absorb 80% of all radiation coming from the sun, generate more than 70% of the oxygen in the atmosphere, act as a vast carbon sink, shape climate and weather, besides supporting the greatest variety of life on earth.

Even before half the life forms that exist in the oceans could be discovered, news about extinction or threat of extinction of different marine life forms started filling headlines regularly. Varieties of species of sea animals and birds are dying everyday because of contamination of their habitats, ingestion of plastics, and congestion of toxic waste and other debris in their surroundings. Oil spills and leaks are adding to the toll.

In many ocean areas, oxygen levels are depleting and ecosystems are getting destroyed. Oceans have started to undergo an increased level of transformation, which has caught even the scientific community unawares and unprepared for damage control. Ocean pollution is one of the major reasons behind this transformation, and it is quickly spreading shore to shore.

More than 80% of ocean pollutants come from land-based activities, but the fact remained ignored for a long time. When human deaths occurred as a result of ocean pollution, governments and the public could no longer feign a mild interest.

A factory in Japan was discharging waste containing methyl mercury in low concentrations into the sea. Ignorant of the biodiversity and interdependence of ocean life forms, the factory owners never imagined that these pollutants would pass through food chains and affect fish and other sea animals. 649 persons died from eating fish and shellfish contaminated with mercury and 3500 people suffered from mercury poisoning. This was just the beginning of many more such incidents across the world.

Pollutants reach the ocean through air, runoffs, deliberate dumping, and accidental leaks, threatening the planet's ecological stability, and therefore, our life support system. Sewage, industrial waste, plastics, radioactive waste, and oil leaks, seeps and spills enter our oceans daily, wiping out ecosystems.

The magnitude of the impact of ocean pollution still remains unknown to many.

Millions of tons of toxic substances are being dumped into the oceans every year. They not only contaminate the habitats of marine creatures but also cause algal blooms that clog up the waterways, destroying entire ecosystems, creating 'dead zones'.

In the Gulf of Mexico there is a low-oxygen "dead zone" the size of Massachusetts. It is estimated that there are nearly 150 dead zones in the oceans; the areas ranging from one square mile to 45,000 square miles, as per a UN Environment Program report.

Fossil fuel burning releases excessive carbon in the earth's atmosphere. Over the last two centuries, this activity has increased significantly, and caused increased acidity in the oceans. This combined with the effects of global warming, has affected the ability of oceans in absorbing greenhouse gases. Ocean acidification has reached a level that is irreversible.

Plastic pollution is a major threat to wildlife in the ocean. It is said that 60 percent of the litter that enters the oceans every year are materials of plastic composition. More than 1 million seabirds and 100,000 other marine animals, including endangered species, have been estimated to die as a result of having swallowed plastic litter or been caught in it.

Though all forms of ocean pollution are taking its toll, one of the most hazardous is oil pollution.

More than 60 million gallons of oil ends up in the oceans every year, however, most of the time it is never reported. Many tankers illegally wash out their holds, miles away from the ports, and it is very difficult to identify the wrongdoers. More than fifty percent of oil pollution caused by ships and tankers are estimated to be deliberate and illegal.

Oil pollution has far reaching consequences. Small quantities of oil spread across long distances to form deadly oil slicks. When a sea bird lands in a slick, the oil coats its feathers, affects its resilience and makes it unable to fly away. It dies slowly. Even slightly oiled birds fall victims when they preen their feathers; in doing so, oily substances, which are poisonous to them, enter their insides. If fishes or birds eat an animal killed by ingesting oil, they in turn are also poisoned, and die. Oil pollution seriously affects marine biodiversity and kills tens of thousands of sea creatures every year.
The Baltic Sea:  The pollution in the Baltic Sea, which is mostly surrounded by land, has reached a highly critical level. Accidental and intentional minor oil spills occur by hundreds every year. In the latter half of the twentieth century, there were around 40 oil spills releasing more than 100,000 tons of oil in the Baltic Sea. Toxic waste also started filling the Baltic Sea in increasing quantities during the same period.

The result, there is no oxygen in 50% of the Baltic's bottom. Populations of a variety of sea creatures have decreased by more than half, and some by three fourths. Humans living around the Baltic have also not escaped from the poisoning of the Baltic waters. An increase in the number of diseases around the Baltic coast is a result of the pollution.

Countries surrounding the Baltic started to coordinate their policies to control marine pollution in the late 1970s. Various committees, conventions and conferences have been organized, including The Oslo Commission, the Helsinki Commission, and the North Sea Ministerial Conferences, to reduce pollution. It is said that there has been a reduction of more than 50% of certain types of toxic pollutants in the Baltic Sea, as a result of these efforts.

The Aral Sea:  The Aral Sea which used to be the fourth largest inland body of water is now the eighth largest. With the reduction in water quantity, salinity rose to toxic levels, and over 500 species of birds, 200 species of mammals, and 100 species of fish died over the past four decades. The health of the people living near the Aral Sea is one of the most significant factors of the Aral Sea crisis. Around five million people are estimated to have been devastated by the crisis. The World Bank and UN are making the most of efforts to improve conditions and address environmental and health problems in the basin.

As  author Peter Benchley said, if man doesn't learn to treat the oceans with respect, man will become extinct. All is not lost yet. It is till possible to turn things around for the ocean. Marine life and ecosystems can be saved by effective recovery programs.

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