Analysis of Northwestern Montana Lakes Based on Transparency and Temperature

Abstract

Lakes exhibit physical, chemical, and biological differences in their responses to climate change. Water transparency and temperature trends have been established as indicators of the quality of lakes in local and regional studies. To better understand responses of lakes to large-scale climatological changes, lakes near Glacier National Park have been regularly monitored through the Northwest Montana Lakes Network since 1992. Citizen science volunteers measured Secchi disk depths and temperature in 47 lakes in Montana, USA, to assess water quality and the potential impacts of climate change on lakes between June and August from 1992 through 2021. We modeled seasonal and annual variability in measurements across years, and among months while accounting for lake-specific variation in seasonal and annual trends. Both Secchi disk depth and temperature changed significantly across all lakes during this period. Secchi disk depth increased significantly in five lakes, and temperature increased significantly within twenty-six lakes. Lakes that were colder on average displayed greater increases in temperature than warmer lakes, and lakes with lower-than-average Secchi depths increased in clarity more than clearer lakes. Future analyses will be conducted on nutrient data received from these lakes to formulate a comprehensive analysis of trophic shifts coincident with climate change.