• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

Ocean Dead Zones Doubling In Size At Alarming Rate

Posted on: Friday, 15 August 2008, 10:47 CDT

Areas of the world’s oceans known as “dead zones” because they lack proper oxygen levels to sustain most marine life, continue to grow worldwide at an unprecedented rate, scientists reported on Thursday.

Scientists point to runoff of nitrogen and phosphorous-containing agricultural fertilizers as the primary cause of the recent expansion.

Nitrogen compounds from burning fossils fuels, particularly from power plants and cars, also are settling back to the ground and eventually wash into coastal waters, said authors Robert J. Diaz of the Virginia Institute of Marine Science and Rutger Rosenberg, of the University of Gothenburg in Sweden, whose report is published in Friday's edition of the journal Science.

The pollution from these runoffs feeds algae which deprive other living marine life of oxygen.

"We have to realize that hypoxia is not a local problem," said Diaz. "It is a global problem and it has severe consequences for ecosystems."

"It's getting to be a problem of such a magnitude that it is starting to affect the resources that we pull out of the sea to feed ourselves," he added.

"If we screw up the energy flow within our systems we could end up with no crabs, no shrimp, no fish. That is where these dead zones are heading unless we stop their growth.”

This decade alone, the number of coastal dead zones has risen by about a third to 405 worldwide, with clusters on the coasts of the United States and Europe. Combined, they take up an area of at least 95,000 square miles.

The newest dead areas are being found in the Southern Hemisphere - South America, Africa, parts of Asia - Diaz said.

The largest dead zone reaches about 30,000 square miles in the Baltic Sea. This is followed in size by one in the Gulf of Mexico starting at the mouth of the Mississippi River in the United States and one at the mouth of China's Yangtze River in the East China Sea.

"It's not sort of a local or regional problem, which is how it was thought of in the past," Diaz said. "It is actually a global problem."

"Most of it is agricultural-based, but there is a lot of industrial nitrogen in there, too, if you consider electric generation industrial," added Diaz.

The number of dead zones began to approximately double every 10 years starting in the 1960s, Diaz and Rosenberg said.

Following the 1990s, there were 301 dead zones, compared to 132 at the end of the 1980s. After the 1970s there were 63, and 39 at the end of the 1960s.

"Farmers aren't doing this on purpose," Diaz said. "The farmers would certainly prefer to have their (fertilizer) on the land rather than floating down the river."

Diaz added that as fertilizers begin to increase in price, farmers may start to consider new methods of retaining them on their land.

Some of the reports are being published for the first time in journals accessible to Western scientists, he said.

Nancy N. Rabalais, executive director of the Louisiana Universities Marine Consortium, said she was not surprised at the increase in dead zones.

"There have been many more reported, but there truly are many more. What has happened in the industrialized nations with agribusiness as well that led to increased flux of nutrients from the land to the estuaries and the seas is now happening in developing countries," said Rabalais, who was not part of Diaz' research team.

"The increase is a troubling sign for estuarine and coastal waters, which are among some of the most productive waters on the globe," she said.

---

On the Net:

• Science
• Virginia Institute of Marine Science
• University of Gothenburg

Source: redOrbit Staff & Wire Reports

More News in this Category