Microbial Source Tracking of Fecal Pollution on Kabushima Beach Utilizing Genetic Markers

Abstract

Microbial source tracking of fecal pollution on Kabushima Beach was investigated using four host-specific genetic markers from May 2014 to December 2016. The numbers of Escherichia coli, total, and fecal coliforms were measured in order to monitor the fecal pollution. During the swimming season, the number of fecal coliforms was lower than 4.0 × 10² CFU 100 mL^-1. In May 2014 and 2015, however, fecal coliform concentrations were very close to1.0 × 10³ CFU 100 mL^-1, which is the upper limit of the Japanese standard value for a swimming beach. The human-, cow-, pig-, and seagull-specific markers were used to identify the sources of fecal pollution. These markers showed 90 to 100% sensitivity and over 80% specificity when tested with sewage and different animal feces. The concentrations of the human-specific marker on the beach were the highest in May, and those of the marker for the black-tailed seagull were high from May to July. In contrast, the cow- and pig-specific markers were not detected. These results suggested fecal contamination on the beach derived from human waste and the feces of black-tailed seagull.