Backcountry Recreation Modeling and the Extent of Human and Canine Fecal Markers in Subalpine Lakes of Mount Rainier National Park

Abstract

Alpine lakes are some of the most fragile ecosystems in our national parks and forests and a focal point of backcountry visitation. As a result of climate change, access to these ecosystems is increasing due to annual reductions in snow cover. This projected extension of shoulder seasons from warming and the increased public interest in national parks and forests creates a confluence of conditions creating concern among land managers. Because of this concern evaluating tools capable of quantifying basin-level visitation and capturing its direct consequence has garnered [more recent] interest. One impact of concern is the infiltration of fecal matter into aquatic systems from unburied waste and leaking privies, which conflicts with principles outlined in the Organic Act of 1916 and the Wilderness Act of 1964. In this study, we sought to evaluate the plausibility of models, parameterized on existing data from Mount Baker-Snoqualmie National Forest (MBS), in estimating basin-level visitation in Mount Rainier National Park (MORA) and, as a consequence of visitation, detect putative human and canine fecal markers in subalpine lakes using microbial source tracking (MST) methods. In MORA, we examined the transferability of a visitation model developed by Wood et al., 2020, and employed MST methods to detect the possible presence of the human-specific and canine-specific Bacteroides (Bacteroidales) markers in 11 subalpine lakes. Here we show that visitation models derived from data outside of MORA lacked transferability compared to the original Wood et al., 2020 study and did not explain enough variation in weekly on-site visitation for accurate estimation in MORA. Though no human-specific marker was detected during the sampling period, these findings do not preclude their presence in the subalpine lakes. Finally, the presence of a canine-specific marker in Upper Deadwood Lake suggests further application of MST methods has value in understanding the pervasion of fecal markers in protected alpine waterways