CORVALLIS, Ore. Healthy streams with vibrant ecosystems play a critical role in removing excess nitrogen caused by human activities, according to a major new national study published this week in Nature.
The research, by a team of 31 aquatic scientists across the United States, was the first to document just how much nitrogen that rivers and streams can filter through tiny organisms or release into the atmosphere through a process called denitrification.
The study clearly points out the importance of maintaining healthy river systems and native riparian areas, said Stan Gregory, a stream ecologist in the Department of Fisheries and Wildlife at Oregon State University, an a co-author of the study. It also demonstrates the importance of retaining complex stream channels that give organisms the time to filter out nitrogen instead of releasing it downstream.
The scientists conducted experiments in 72 streams across the United States and Puerto Rico that spanned a diversity of land uses, including urban, agricultural and forested areas. They discovered that roughly 40 to 60 percent of nitrogen was taken up by the river system within 500 meters of the source where it entered the river if that ecosystem was healthy.
Tiny organisms such as algae, fungi and bacteria that may live on rocks, pieces of wood, leaves or streambeds can take up, or absorb about half of the nitrogen on average that humans currently put into the sampled river sites, according to Sherri Johnson, a research ecologist with the U.S. Forest Service, and a courtesy professor of fisheries and wildlife at OSU.
Streams are amazingly active places, though we dont always see the activity, Johnson said. When you have a healthy riparian zone, with lots of native plants and a natural channel, the stream has more of an opportunity to absorb the nitrogen we put into the system instead of sending it downriver.
The study is important, scientists say, bec
|Contact: Stan Gregory|
Oregon State University