MANHATTAN -- Streams are not gutters that simply deliver nutrients to lakes, oceans and bays. They 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 will be reported in the April 6 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 an 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.