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Other authors of the Science article are

* Jack Webster and Maury Valett, Virginia Tech University

* Jennifer Tank, University of Notre Dame

* Bruce J. Peterson, and W.M. Wollheim, Marine Biology Laboratory

* Patrick Mulholland, Oak Ridge Laboratory

* J.L. Meyer University of Georgia

* E. Marti, Centre d'Estudis Avancats de Blanes, Spain

* W.B. Bowden, Landcare Research, New Zealand

* A.E. Hershey, University of North Carolina

* W.H. McDowell, University of New Hampshire

* S.K. Hamilton, Michigan State University

* Stanley Gregory, Oregon State University

* D.J. Morrall, Proctor & Gamble Company Experimental Stream Facility.

 

Small streams important in controlling nitrogen, preserving water quality

Streams are not gutters that simply deliver nutrients to lakes, oceans and bays.

By Staci Hauschild

 

 

King's Creek closeup
Photo by April M. Blackmon.

 

Streams are vibrant ecosystems, and the smallest streams remove as much as half of the inorganic nitrogen that enters them, according to a Kansas State University researcher who is part of a national group of researchers who studied 10 streams from Puerto Rico to Alaska over the course of three years.

The results was reported in the April 6, 2001 issue of Science, in the article "Control of Nitrogen Export From Watersheds by Headwater Streams," co-authored by Walter Dodds, a K-State associate professor of biology who headed K-State's research team. Kings Creek on K-State's Konza Prairie is the prairie stream studied in the research.

According to Dodds, human activities, such as fertilizer application and sewage disposal result in excess nitrogen entering streams, deteriorating water quality downstream in rivers, lakes and coastal marine habitats. The approach to minimizing nitrogen contamination in these waterways has been mainly terrestrial, since the processes responsible for nitrogen uptake and release in streams has been a black box. But a National Science Foundation-sponsored workshop in 1995 identified models and a nitrogen tracer approach that was used to open the "black box."

Dodds said scientists used the model to create hypotheses and devise the same experiments at each of the different sites. Tracer amounts of ammonium -- a form of nitrogen -- were dripped into the stream over a month. Chemical and analytical techniques were used to follow the ammonium into the various forms of nitrogen as it went into different parts of the ecosystem --plants, animals, etc. -- and how much of it just stayed in the water and washed down. The model was then used to calculate movement of the nitrogen in the individual streams and then to compare the 10 streams.

"What we found at the Konza was the same thing we found at many of the other sites," Dodds said. "When you add the tracer to the streams, within several hundred meters it's all in the stream bottom; it's all been taken up by the organisms that live in the stream.

"The bottom line is streams have an impact. They can remove as much as 50 percent of the inorganic nitrogen. Conservation of small streams is an important step in mitigating the nitrogen that reaches rivers, lakes, bays and oceans."

Dodds said the research "fits in well" with research on what forms a baseline for water quality in Kansas streams.

"The picture we're seeing from our research on the Konza, compared to some of the other streams around the state, is that the water quality in Kansas can potentially be very good with regard to nitrogen," Dodds said. "That is, we can have very low nitrogen values, and the system can be very retentive of the nitrogen that does get in; the natural processes that occur in the prairie, what Kansas mostly was at one point, leading to very good water quality."

According to Dodds, this establishment of a baseline allows regulators to know what's possible in terms of goals for water quality protection.

"This demonstrates that the natural systems out there really allow for very clean water," Dodds said. "It provides a point of comparison that shows we have a lot of water bodies in the state that are highly contaminated with nitrogen."

The research was funded by the National Science Foundation with a $1.4 million grant plus the resources of each unit.

June 2002