Fecal source tracking based on fecal coliform concentration and bacterial community structure in the Bong stream,...

Fecal source tracking of the Bong stream, a representative inland pollutant around the drainage basin of Gangjin Bay (an area where shellfish are grown for export), was performed three times in four confluence areas with 13 sampling sites by analyzing fecal coliform concentrations and two types of bacterial community structures. Identification of the origin of major fecal pollution in the area that inflowed simultaneously via several branch streams was difficult using fecal source tracking based on fecal coliform concentration. Bacterial community analyses using high-throughput sequencing showed that the dominant groups in the entire bacterial community at the class level were Beta-, Gamma-, and Alpha-proteobacteria; Flavobacteriia; and Bacteroidia, and the most abundant groups in the Bacteroidales-specific community at the genus level were Prevotella and Bacteroides. Hierarchical clustering and Bray-Curtis dissimilarity analysis for fecal source tracking indicated that the Bacteroidales-specific community was superior in water environments compared with analysis of the entire bacterial community. Conversely, when the degree of fecal pollution in the sample was low, fecal source tracking based on the entire bacterial community was more reliable. These results suggest that fecal source tracking based on bacterial communities is a useful tool for identifying the origin of fecal pollution in a large stream and implementing systematic guidelines for the establishment of an effective management plan to reduce fecal pollution sources.