Chapter 5 – Nutrient Spiraling and Transport in Streams: The Importance of In-Stream Biological Processes to Nutrient Dynamics in Streams

We developed a computer model to evaluate the effects of in-stream processes on nutrient concentrations and then examined potential climate change effects on these processes. Our model includes stream spiraling, ecological stoichiometry, and autotrophic and heterotrophic processes. We found significant synergistic interactions between microbes that immobilize nutrients and microbes that mine nutrients from detritus. Algae and microbes often competed for critical nutrients, but there was evidence of some synergistic interaction during parts of the year. Elevated temperature increased both net primary production and leaf decay, but net nutrient uptake was reduced. Elevated nutrients illustrated dual nutrient limitation. Because of the strong land-water linkages of streams, more complete analysis of potential climate change effects on streams would need to include both direct and indirect climate change effects through changes to terrestrial vegetation. What happens in streams cannot be ignored, either for studies of watershed nutrient dynamics, or for evaluating climate change effects on stream chemistry.