Using Watershed Characteristics for Improving Fecal Source Identification

Abstract

Fecal pollution is one of the most prevalent forms of pollution affecting waterbodies worldwide, threatening public health, and negatively impacting aquatic environments. Microbial source tracking (MST) applies polymerase chain reaction (PCR) technology to help identify the source of fecal pollution. In this study, we combine spatial data for two watersheds with general and host-specific MST markers to target human, bovine, and general ruminant sources. Two different PCR technologies were applied for quantifying the targets: quantitative PCR (qPCR) and droplet digital PCR (ddPCR). We found that ddPCR had a higher detection rate (75%) of quantifiable samples compared to qPCR (27%), indicating that ddPCR is more sensitive than qPCR. The three host-specific markers were detected at all sites (n=25), suggesting that humans, cows, and ruminants are contributing to fecal contamination in these watersheds. MST results, combined with watershed characteristics, suggest that streams draining areas with low-infiltration soil groups, high septic system prevalence, and high agricultural land use are at an increased risk for fecal contamination. Microbial source tracking has been applied in numerous studies to aid in identifying the sources of fecal contamination, however these studies usually lack information on the involvement of watershed characteristics. Our study combined watershed characteristics with MST results, applying more sensitive PCR techniques, in addition to watershed characteristics to provide more comprehensive insight into the factors that influence fecal contamination in order to implement the most effective best management practices. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/496426v2_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@13ca50forg.highwire.dtl.DTLVardef@78a781org.highwire.dtl.DTLVardef@13d0664org.highwire.dtl.DTLVardef@16ec950_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIddPCR provided higher sensitivity over qPCR when analyzing environmental samples C_LIO_LIHuman markers had an association with the number of septic systems in a watershed C_LIO_LIEvery site had positive detections for all FIB markers C_LIO_LIBoth ruminant markers were associated with low infiltration hydrologic soil groups C_LIO_LICombining watershed characteristics with MST testing improved source identification C_LI