s for animals. The explosion in plant life lead to lots of rotting plants, which suck up all the dissolved oxygen or can release toxins.

(Satellite Pic)

The Mississippi Delta

Picture: NASA/SeaWifs |

There is a large dead zone at the mouth of the Mississippi River, above, that has been caused by nutrients that have been washed down the river.

"The development of toxin-producing algae in marine environments is a threat to human health when accumulating in fish, particularly shellfish," report A. F. Bouwman and colleagues at the Netherlands Environmental Assessment Agency. Their paper on the changes in dead zones appears in the current issue of the journal Global Biogeochemical Cycles.

The large dead zone at the mouth of the Mississippi River, for example, is an area loaded with nutrients that have been washed down the river, with a great deal of nitrates coming from intensive agriculture in the Midwest, said William Mitsch, professor of natural resources at Ohio State University.

There are about 150 such dead zones worldwide. Many are expected to see changes from increased agriculture inland or simply human population growth that is racing ahead of the capability to treat sewage.

Bouwman's team used historical information about changes in land use and population growth, along with projections on land use, to come up with a simulation that shows how much and where nitrogen compounds are expected to expand marine dead zones.

"Our results for the time period 1970-2030 indicate rapid increases in river (nitrogen) export for the Indian (46 percent) and Pacific (38 percent) oceans, and a slower increase (six percent) for the Atlantic Ocean," Bouwman concluded.

Developing countries are expected to follow the same trend as in the last three decades — a 27 percent increase in nitrogen.

But it's not just about fish. The nutrient-bloated waters pouring out of rivers may be chemically predisposed to favor the most poisonous algal blooms in the seas because of something happening upstream: dams.

It turns out that dams may be holding back significant silica that usually would reach the oceans. That silica is needed by microscopic diatoms to create their glassy bodies.

"When diatom growth is compromised by (silica) limitation, non-diatoms may be competitively enabled," Bouwman explained.

That leaves the door open for their competitors: flagellated algae that include the noxious "red-tide" bloom-forming organisms.

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Jeffrey Scott Flesher Medically Retired U.S. Air Force: Disabled Gulf War Veteran

Jeffrey@myremoteaccess.com

http://www.vetshelpcenter.com/

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