Global change encompasses many factors that affect the capacity of ecosystems to retain and process carbon, including changes in nutrient delivery. We determined the effects of experimental long-term nutrient enrichment (N+P addition for 5 years compared to a reference) on the capacity of a headwater stream to retain particulate carbon.  We hypothesized that nutrient enrichment would accelerate FPOM export due to increased breakdown of CPOM by microbes and macroinvertebrates. We found trends largely consistent with predictions: cumulative export of FPOM and CTOM was higher in the treatment vs reference stream following enrichment.  Annually, export was higher in the treatment vs reference stream in yr2, yr3, and yr4 of enrichment, but that trend was reversed in yr5, when relatively more organic matter was exported from the reference stream.  Progressive declines in leaf litter standing crop (as a function of stored carbon plus annual inputs) may have led to less generation of FPOM while increased filterer production may have promoted FPOM retention in the treatment stream by yr5 of enrichment.  Our data on temporal dynamics and other biological and physical measures will help in developing predictive models of how nutrient enrichment affects carbon retention in detritus-based ecosystems.