Coupled production between algae and bacteria in stream epilithon was assessed along a nutrient-enrichment gradient in 8 Texas streams with open canopies. Photosynthesis (PS) and bacterial biomass production (BBP) were measured simultaneously using a dual-label radioassay (¹⁴C-HCO₃^– uptake and ³H-L-leucine incorporation into protein) on multiple samples within a stream reach. PS and BBP were measured after light (1200–1500 μmol m⁻² s⁻¹) and dark incubations. The degree of coupled production between algae and bacteria within a stream was estimated as the covariation (i.e., correlation or covariance) between PS and BBP derived from unshaded replicates in each stream. Streamwater nutrients ranged from 0.18 to 8.1 mg/L total N and 0.009 to 2.0 mg/L total P. Epilithon N and P content (as % dry mass) and C:N:P ratios varied widely among streams and were positively correlated with streamwater nutrient concentrations. Mean BBP measured in light incubations (BBP_L) was greater than mean BBP measured in dark incubations (BBP_D), and the difference between the 2 means (BBP_L – BBP_D) was positively correlated with mean PS among streams (R² = 0.53). Covariance between PS and BBP_L within streams (COV_PS–BBP) decreased as epilithon nutrient content increased. COV_PS–BBP was positively correlated with both epilithon C:N (R² = 0.78) and C:P (R² = 0.77) among streams. These results suggest that algal and bacterial production are decoupled by nutrient enrichment, and that algae might rely more heavily on bacterial-regenerated nutrients than on streamwater nutrients to support production in nutrient-poor streams.