Polluted rivers threaten Gulf of Mexico

Lynne Kozarek

The Mississippi and Minnesota Rivers are making a killer contribution to the Gulf of Mexico, say University researchers. C. Ford Runge said the rivers are the source of 70 percent of the pollutants contributing to a dead zone in the Gulf of Mexico.
Runge, a University professor of applied economics, spoke at the Governor’s Summit on Agriculture in December and revealed that the two rivers are contributing the majority the total toxins delivered to the gulf.
The affected area is commonly called the dead zone, but the scientific community refers to the oxygen-depleted area as “hypoxic.” For an area to be considered hypoxic it must contain oxygen levels below two parts per million.
Runge also said that huge populations of shellfish and crustaceans are being killed off by the low levels of oxygen in the dead zone.
“The hypoxic zone shows the extent to which agriculture can impact ecological condition,” Runge said. “This is an example of transboundary pollution.”
The substances causing the polluted waters are found naturally in soils, but in low levels. Nitrate nitrogen and phosphate are also found in fertilizers and manure.
The polluting chemicals run off into the rivers and provide excess nitrogen, which algae feed upon. The algae then consume oxygen, which is needed by fish and other marine creatures for survival.
The dead zone is located at the mouth of the Mississippi River, where it flows into the Gulf of Mexico. The size of the zone of hypoxic water varies from year to year, but worsens from mid-May to mid-September because of seasonal changes, such as melting snow.
“The size of the hypoxic zone has grown substantially over the past few years,” Runge said.
Human populations could also be affected by the toxic waters, Runge said.
Although the connection between specific health problems and the hypoxic waters are not entirely clear, “there are strong links between pollution and mortality,” Runge said.
Actions are being taken to correct this problem and prevent it from affecting other areas.
“There is a very substantial reason to believe that filter strips can be used to buffer these areas,” Runge said.
Filter strips are areas of trees, grass and natural vegetation planted close to the banks of streams to keep fertilizer runoff from entering the water in such large quantities.
There are several departments at the University that are involved in cleaning up the pollution in the Minnesota River that affects bodies of water thousands of miles away.
“I don’t think there is an organized University effort,” Runge said, “but various departments are involved with the Minnesota River project.”
The Minnesota River Basin Joint Powers Board was formed in 1995 to help coordinate people to work together in watersheds. The board also works to educate the public about the pollution in the Minnesota River.
Ken Albrecht, chairman of the Joint Powers Board, said that the committee is also examining ways to clean up the pollution.
“It took 150 years to pollute the river,” Albrecht said, “we won’t turn it around immediately.”
The Joint Powers Board is also working with the University Extensions Service to clean up the Minnesota River.