In 1994 researchers at Ohio State University created two artificial wetlands* in riverine basins in order to investigate their possible benefits, and whether they could replace those lost to environmental degradation. A key benefit would be the cleaning and filtering of polluted water.
The Mississippi watershed, like many other watershed regions, is affected by chemicals that turn about 7000 square miles of the Gulf of Mexico into a so-called 'dead zone'. This dead zone suffers from hypoxia, a condition that occurs when nitrates and phosphorus from fertilizers cause excessive growth of algae. These algal blooms deplete the water of almost all oxygen, making it dangerous for fish and other animals. Ohio State University wanted to find out if the design of these artificial wetlands would work.
Apparently it did. "It was a relatively simple, inexpensive way to create a wetland, and it worked," said William Mitsch, who is the director of the Olentangy River Wetland Research Park at Ohio State University and professor of natural resources. He describes how the wetlands were made by shoving a series of basins into the original area, placing them downward on the slope towards the river. The fifth basin would be the highest one. The water of the river would come into the first basin and slowly drip into the others, so they were all connected by water flowing beneath the surface.
In the first wetland, Mitsch and his colleagues placed thirteen different types of plants. In the other one they let nature grow by itself, so they could see the difference between naturally grown plants and planted ones. After fifteen years of close inspection, it turned out the planted wetland had a taller plant community, but the unplanted wetland was more productive.
In two years, they "...saw a pretty significant reduction in phosphorus and nitrate concentrations – close to the kind of decrease we typically see in a natural wetland." Mitsch emphasizes that artificial wetlands can save money, since they require less investment in water purification systems. Still, while the American Midwest has lost 80 percent of its wetlands in the last two centuries, only 577,000 artificial wetlands have been created. According to Mitsch, 10 to 25 times that many are needed in the Mississippi in order to see a significant improvement in the Gulf's situation.
*Swamp-like areas that act as buffer zones between land and waterways.