Recovery of aquatic bacterial populations in a stream after cessation of chemical pollution

The authors studied Tims Branch, located on the Savannah River Project in Aiken, S.C. Until 1973, 229,900 kg of chemicals were discharged annually into the fast-flowing stream. From 1973, a two-year study of the stream's recovery, using an adjacent unpolluted stream as a control, was carried out. Total culturable bacterial counts and diversity were used as indices of recovery. Diversity in both streams was more affected by seasonal temperatures than by the presence of chemical pollution. Mean total counts in the polluted stream dropped, following cessation of pollution, to approximate those of the control stream. (PJR)