Year: 2026
Type: preprint
Abstract: Coastal waters often experience fecal contamination from human (e.g., septic systems, wastewater treatment catchments and outfalls) and non-human (e.g., wildlife, domesticated pets, and livestock) origins, posing human health risks through contaminated fisheries and recreational waters. Quantitative PCR (qPCR) methods can identify and quantify fecal origins for their management by targeting Bacteroides , a dominant group of gastrointestinal bacteria with high host specificity. This study identified major contributors and drivers of fecal contamination to Mobile Bay, Alabama, an urbanized estuary in the southern United States. We utilized a multi-species qPCR source tracking approach targeting total Bacteroides and human-, pig-, dog-, cow-, and fowl-associated Bacteroides . Water samples and environmental parameters were collected over one year from 13 sites that represent a range of potential fecal inputs common to coastal waters. Human-associated feces were a consistent major contributor to the system (positive in 82% of samples), with localized inputs from pig (wild or domestic) and dog. Freshwater discharge and nitrogen constituents were good predictors of Bacteroides concentrations in this system, while areas with impervious surfaces and developed land cover may be contributing elevated fecal indicator levels. The multi-species qPCR source tracking approach described in this study can be implemented in other watersheds to support the development of better detection, identification, and fecal management strategies for community health of coastal areas. Importance (<150 words; nontechnical explanation of the significance of the study to the field) Humans, wildlife, domesticated animals, and livestock may contribute to fecal contamination of coastal waters. Fecal contamination can pose human health risks by making fisheries and recreational areas unsafe. To successfully mitigate fecal contamination, the origin (biological source) of feces needs to be known. We identified fecal origins to an urbanized estuary using a DNA-based approach that targets multiple potential fecal contributors through their associations with gut bacteria ( Bacteroides ). Our data set a baseline for fecal origins and concentrations in the Mobile Bay estuary and represent the most spatially and temporally comprehensive microbial source tracking effort in the region to date. Due to robust simultaneous cross-validation, this study also represents the first successful application of this source tracking approach for analysis of five species from the same sample. This approach is broadly transferrable to inform management and improve community and ecosystem health.
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221070524