Significance of several bacteriophage groups as indicators of sewage pollution in marine waters

Abstract

Seawater samples collected from two beaches with different levels of pollution were studied for the presence of classically and newly proposed faecal indicators such as, total and faecal coliforms, faecal streptococci, coliphages, F-specific phages and bacteriophages of Bacteroides fragilis. Total and faecal coliforms showed lower survival rates in seawater than faecal streptococci, F-specific bacteriophages and coliphages. On the other hand, total coliform concentrations were only higher than those of faecal coliforms in heavily polluted seawater, although in samples with a low level of pollution, faecal streptococci and Escherichia coli C phage counts were generally greater than those showed by faecal coliforms. The low concentration in which F-specific and B. fragilis bacteriophages were detected in marine waters compared to the E. coli bacteriophage levels, is an important shortcoming for the general use of the former microorganisms as universal indicators of faecal pollution. From the results obtained in this study, it may be concluded that faecal streptococci and E. coli C bacteriophages are the most appropriate indicators of the remote pollution in marine waters.