Hamilton, S. K., J. L. Tank, D. F. Raikow, W. M. Wollheim, B. J. Peterson, and J. R. Webster. 2001. Nitrogen uptake and transformation in a midwestern U.S. stream: A stable isotope enrichment study. Biogeochemistry 54:297-340.
This study presents a comprehensive analysis of nitrogen (N) cycling in a second order forested stream in southern Michigan that has moderately high concentrations of ammonium (mean, 16 g N/L) and nitrate (17 g N/L). A whole-stream 15NH+ addition was performed for 6 weeks in June and July, and the tracer 15N was measured downstream in ammonium, nitrate, and detrital and living biomass. Ancillary measurements included biomass of organic matter, algae, bacteria and fungi, nutrient concentrations, hydraulic characteristics, whole-stream metabolism, and nutrient limitation assays. The results provide insights into the heterotrophic nature of woodland streams and reveal the rates at which biological processes
alter nitrogen transport through stream systems.