Distribution of autotrophic nitrifying bacteria in a polluted river (the Passaic).

The abundance of nitrifying bacteria, determined by most-probable-number procedures, within habitats of the Passaic River was as follows: rooted aquatic plants greater than algae approximately equal to rocks greater than sediments greater than greater than water. On the average, NH4+ oxidizers were 540-fold more abundant in the topmost 1 cm of sediment than in the water, and NO2- oxidizers were 250-fold more abundant. The population densities in this surface sediment at two nearby stations, one with a predominantly mineral stream bed and the other an organic ooze, did not differ significantly. Large numbers of nitrifiers were present to a depth of about 5 cm in a mineral sediment core.