Physico-chemical conditions and community metabolism in the relatively undisturbed and unpolluted Blue River, a tributary of the Red River in southeastern Oklahoma, are described. Water temperatures, streamflow, oxygen exchange rate, pH, conductivity, turbidity, alkalinity, chlorides, sulfates, organic matter, chlorophyll a, and diurnal dissolved oxygen were measured. Seasonal environmental changes, effects of channel strata upon community metabolism, and the efficiency of photo-autotrophic organisms in converting solar to chemical energy were determined.