Jody D. Potter, Research Technician III & M.S. student
Natural Resources: Water Resources

Research Title: Characterizing rates and mechanisms of nitrate retention with change in land use in tropical rainforest streams

Advisor: Dr. Bill McDowell

Description of Research

Nitrogen (N) loading of terrestrial and aquatic ecosystems is increasing worldwide as a result of human activities, leading to eutrophication of estuaries and coastal marine ecosystems. Mass balance studies show that a significant portion of the N load does not make it to coastal systems and recent studies suggest that small, headwater streams are important sites for N processing and retention.

This is an intensive study of the fate of nitrate in headwater tropical streams. The research will evaluate the factors controlling nitrate uptake and retention and how human disturbances affect those factors. We will use field 15N-nitrate tracer experiments to determine the rates and factors controlling nitrate uptake and retention in relatively undisturbed streams, and in streams that have been altered by agriculture or urban development and have elevated nitrate levels.

The study site will be in Puerto Rico and will be part of a much larger study called the Lotic Intersite Nitrogen eXperiment (LINX) II. The LINX II study will have eight sites across the US in a diversity of biomes. Each site will have 3 reference (native vegetation), 3 agricultural and 3 urbanized streams of which 15N-nitrate addition experiments will be performed in 72 1st to 3rd order streams. The results from all of the biomes will be used to develop a model of nitrate retention in streams and will be combined with GIS information on hydrography and land use to predict nitrate retention in larger river basins at all of the study sites.