Development of U.S. nutrient criteria has focused on stressor-response relationships associated with algae, but lakes and streams differ in the extent that algae vs terrestrially-derived detritus fuels food webs and ecosystem functions. Terrestrial carbon dominants energy flow in most stream ecosystems and is quantitatively related to the production of organisms and uptake of pollutants. Thus, it is important to quantify the effects of nutrients on terrestrial carbon resources in streams. Our previous studies have shown that elevated concentrations of nutrients in streamwater resulted in increased nutrient content of detrital materials and associated higher loss rates of detritus through microbial decomposition and feeding by detritivores. Increased nutrient loading reduced annual standing stocks of carbon in streams and resulted in greater seasonal variability in carbon, nitrogen, and phosphorus standing stocks. Downstream transport of nutrients via nutrient-accelerated loss rates of terrestrial carbon may be a source of increased nutrient loading to downstream systems. These impacts may occur through changes in the nutrient content of detrital materials, coupled with greater mineralization rates of nutrients and carbon, have not been explored.
Results/Conclusions
Here we summarize the ranges in terrestrially derived carbon standing stocks in stream ecosystems and estimate the impacts of carbon loss and nutrient retention to downstream ecosystems using a simulation model of detrital decay. We predict that models with elevated vs baseline streamwater nutrient concentrations result in greater temporal variability in uptake and release of nutrients to downstream systems. We will explore how microbial stoichiometric plasticity, nitrogen and phosphorus concentrations, and temperature affect nutrient export. Our analyses can inform management by illustrating the potential loss of ecosystem services caused by nutrient pollution that likely occur through carbon-nutrient interactions resulting in accelerated carbon mineralization and associated nutrient transport.