Diurnal Variability and Sources of Coliphage, Enterococci and Non-Typhoidal Salmonella in a Tidal Beach

Earlier studies presented poor relationships between enterococci and waterborne pathogens and coliphage has been suggested as an alternative fecal indicator. The majority of eastern U.S. beaches have semidiurnal tidal cycles which can influence water quality at various times of the day. The purpose of this study was to compare the hourly and seasonal occurrence of Enterococci, coliphage, and non-typhoidal Salmonella at a tidal beach (JK3) and an adjacent creek (JK1) on Jekyll Island, Georgia. Samples were collected every hour in January and July 2016. Culture methods were utilized to enumerate Enterococci (Method 1600), somatic and male-specific coliphages (Method 1602) and non-typhoidal Salmonella (Method 1200). In-situ collected environmental data (temperature, salinity, pH, dissolved oxygen, turbidity, tide height, and three days of cumulative precipitation) were compared with microbial data. Among all microorganisms, only male-specific coliphage and Enterococci presented a significant correlation (p<0.05) at the beach. Both Enterococci and male-specific coliphage concentrations (1-41 PFU/100 ml) elevated during the day as high tide conditions occur at the beach. Seasonality was only observed within male-specific phage, and their levels were greater in the summer than winter. Tides influenced the somatic coliphage means, and their concentrations decreased from 71±1.8 PFU/100 ml during low tide to 20±5 PFU/100 ml during high tide in the creek. Among environmental factors, water temperature and male-specific phage were significantly correlated (p<0.05). Salmonella as a waterborne pathogenic bacteria was only detectable in the creek (with a maximum of 26 MPN/100 ml) and significantly decreased below detection limits by the time they reach to the beach. Further studies are needed to investigate the relation between enteric viruses and coliphage, and environmental factors affecting phage ecology. This study shows that male-specific coliphage has a potential to be utilized as an alternative indicator at tidal beaches.