River bottom sediments, which were washed free of loosely associated chemical nutrients, were further eluted with phosphate buffer. Chemical analyses of the eluates indicated that 0.3 M buffer (pH 7.0) eluted hexose, protein, and ammonia nitrogen in concentrations 4–6 times that found in the free-flowing water. Respiration experiments showed that selected strains of Enterobacteriaceae, including pathogens, had the ability to metabolize these substrates. These studies indicate that bottom sediments can have a high adsorptive capacity and suggest that they can regulate basic nutrient concentration and eutrophication in situ.