No abstract

In a l‐year study at Ironbridge on the Welsh River Dee the Escherichia coli popu‐lation varied over a 200‐fold range and the coliphage populations grown at 37°C (H. T. phage) and at 22°C (L. T. phage) each varied by over 100‐fold. Both the E. coli and H. T. phage counts were shown to have highly signiflcant seasonal fluctuations, which included troughs in summer and peaks in winter. The L. T. phage count appeared to maintain a baseline population in summer and had a 20‐fold less sig‐nificant association with temperature than the H. T. phage population.