Soil: The environmental source of <i>Escherichia coli</i> and enterococci in Hawaii's streams

Abstract

Abstract The concentrations and sources of Escherichia coli and enterococci in a typical stream (Manoa) in Hawaii were determined. The concentrations of these two sanitary indicator bacteria in Manoa Stream consistently exceeded the new U.S. Environment Protection Agency recreational water standard in freshwater of 126 E. coli /100 mL or 33 enterococci/ 100 mL. Escherichia coli but not enterococci was shown to multiply in stream water samples. Soil samples obtained near the stream bank, 10 m from the stream bank as well as from a grassy area on the university campus, were determined to be sources of both E. coli and enterococci. These indicator bacteria were recovered from the surface of the soil as well as from soil samples at depths down to 36 cm. Soil is considered the most likely source for the high concentrations of indicator bacteria naturally present in the freshwater streams of Hawaii.