A cotton-strip assay was used to measure decomposition rate and nutrient uptake by decomposing microbes (i.e., immobilization) within 19 streams across the Chattahoochee and Ocmulgee River Basins in Metropolitan Atlanta, Georgia (USA). Decomposition rates were strongly correlated to phosphorus immobilization rates suggesting that nutrient supply influenced carbon cycling. Using GIS and satellite imagery, we analyzed land-use patterns to identify potential sources of phosphorus. The overall impervious cover was positively correlated with decomposition and phosphorus immobilization, but much stronger relationships were observed with low-intensity residential land areas. This suggests that increased rates of decomposition and immobilization could be due to lawn fertilizer application or an aging water infrastructure. Our study shows strong linkages between nutrient and
carbon cycles in urban streams.