Hikers Impact on the North Fork of the Virgin River, Zion National Park, Utah

Abstract

The research studied the benthic algal cyanobacterial community and ecological and physical characteristics to determine whether recreational hiking impacts the Virgin River in Zion National Park, Utah. Sampling occurred on 10 August 2001 of three cobblestones from 11 different riffle locations. The null hypothesis is the algal community will change in assemblage structure and function along a hikers gradient. This hypothesis predicts that lower or no visitor use sites will have lower algal species diversity, average cell biovolume, cell density, total biomass, chlorophyll a, AFDM, and ash weight and percentage. There were 99 benthic algal and cyanobacteria species identified from the Virgin River. The benthic flora and ecological/physical parameters were examined to assess the impact of hiking. Canonical correspondence analyses of the species data separated sites into 2-groups (impacted and none to low impact). The first and second axes of the ecological/physical variables explained 67% of the variation. The average cell biovolume and species diversity were positively aligned to the first axis, while cell density was slightly negatively aligned. The data suggests the ecological threshold had been reached lowering the relative abundance of diatoms and increasing cyanobacteria contribution. Further research needs to be accomplished determine exact cause.