Use of microbial fecal indicator monitoring and fecal source tracking as a park management tool in Rocky Mountain National Park

Visitation to national parks in the United States increased by an estimated 9,304,786 visitors from 2018 to 2019. This increased visitation has resulted in negative impacts to protected natural resources. Visitor use impacts include contamination of surface waters with fecal waste which may contain pathogenic microorganisms. In this study we evaluated the use of fecal indicator bacteria approach and microbial source tracking as a park management tool to (i) identify potential public health threats in recreational water bodies; and (ii) characterize visitor use habits throughout Rocky Mountain National Park. Traditional fecal indicators including E. coli, fecal coliforms, and total coliforms were utilized as well as antibiotic resistant bacteria. Fecal indicator bacteria and antibiotic resistant bacteria were present in all water bodies located in high visitation areas. Trends in fecal indicator bacteria and antibiotic resistant bacteria concentrations correlated with visitor use metrics, suggesting those could be markers for characterizing visitor use and impact within the park. We also present a case study of the use of these indicators for park management by assessing the efficacy of two pit toilet types on inhibiting fecal waste from entering downstream surface waters. A new urine diverting toilet did not consistently prohibit coliforms, antibiotic resistant bacteria, or human-associated fecal genetic markers from entering downstream surface waters as compared to a traditional pit toilet or areas with no upstream pit toilet. The use of microbial fecal indicator monitoring offers a two-fold data acquisition opportunity for park managers to address potential public health concerns while characterizing visitor use.