Spatiotemporal variability in microbial water quality and fecal source tracking markers in a subtropical estuary and its tributaries

In rapidly developing urban communities, recreational water quality is often compromised by the presence of fecal pollution, increasing the potential risk to public health. In this study, surface water samples from tributaries to Lake Pontchartrain (an estuary in southeastern Louisiana, United States), recreational shoreline sites, and wastewater samples from residential aerobic treatment units (ATU) were collected and analyzed for fecal bacteria using both culture- and molecular-based assays. During the 2-year study period, fecal indicator bacteria (coliform, <i>Escherichia coli</i>, and enterococci) were detected in all water samples collected from tributaries. Human-specific fecal marker concentrations varied per sampling site but were significantly higher in tributaries, demonstrating individual wastewater treatment units as a primary source of fecal contamination. Pathogenic <i>E. coli</i> and <i>Campylobacter jejuni</i> were only detected in tributaries. Statistical analysis indicated weak relationships between physiochemical water quality parameters and concentrations of enteric pathogens or fecal markers. The prevalence of human fecal contamination in estuaries poses a potential public health problem for recreational use, as it increases exposure risks. This study demonstrates that the application of multiple water quality indicators may yield greater confidence in assessing fecal contamination and ultimately could better inform remediation decisions to improve recreational water quality.