Factors affecting nitrification in situ in a heated stream

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Abstract
Nitrification, previously shown to occur in the stream under study, ensued only when the stream received heated (.gtoreq. 28.degree. C) discharges and was negligible when water temperatures were .ltoreq. 17.degree. C. The most probable number of ammonium oxidizers in stream bed sediments exceeded nitrite oxidizers by ratios of 43:1 to 1113:1, and the average rate of ammonium oxidation in this stream, 0.50 mg of NH4-N/l per h exceeded the rate of nitrite oxidation, 0.29 mg of NO2-N/l per h, resulting in an accumulation of nitrite. Nitrification rates were influenced by the dissolved O2 concentration, increasing during daylight hours and exhibiting maximum rates during the summer.