Dissolved organic carbon fluxes in the Shetucket River of eastern Connecticut,U.S.A.*

SUMMARY. Seasonal changes in dissolved organic carbon (DOC) concentrations were monitored biweekly for 1 year at seven stations in the Shetucket River watershed in eastern Connecticut, U.S.A. Nine monthly diurnal studies revealed 24-h fluctuations of up to 53% of the seasonal range of 250–2200 μm DOC. Net DOC removal along a 1.9-km stretch below a secondary sewage treatment plant (activated sludge effluent diluted to a final average volume of 1.4% in the river) ranged from 0 to 1600 and averaged 68 ± 64 mmol m^?2 day^?1. Removal of DOC further downstream could only be observed during a severe 3-h October storm when net uptake ranged from 16 to 92 mmol m^?2 h^?1, using upstream-downstream techniques. Oxygen respiration could account for about half of the net DOC removal during the October storm. Even though net uptake was somewhat greater than reported in other lotic studies, about 97% of the DOC potentially available to benthic heterotrophs was exported further downstream.