GSA Connects 2021 in Portland, Oregon

Paper No. 113-12
Presentation Time: 4:40 PM


BONNER, Hannah, Department of Geological Sciences, University of Colorado Boulder, Boulder, CO 80309

Toxigenic cyanobacteria were first identified in Zion National Park in July 2020. These cyanobacteria form benthic mats in the Virgin River and release cyanotoxins including anatoxin-a, cylindrospermopsin, and nodularin. These toxins may be hazardous to human and animal health and have proven a major management concern for popular in-water park activities. Benthic cyanobacteria have received limited attention in the literature however, with the Virgin River only the second water body in the United States to have identified toxigenic benthic species. Working under the Scientists in the Parks Fellows program, I created an expanded monitoring program that collected water quality data, cyanobacteria coverage percent, and two different toxin concentration measurements on a weekly or bi-weekly basis. Citizen science outreach was also developed to better understand the historic presence of benthic mats. Resulting data was used to examine seasonal and temporal trends in cyanobacteria distribution and toxin production. Cyanobacteria mats were found to be most prolific in warm, sunny conditions with low river turbidity. Mat coverage and cyanotoxin production spiked in summer months and decreased significantly in winter. A high flow event temporarily reduced coverage percent, but it is predicted that successive events are required to maintain cyanobacteria reduction. These findings were used to update park monitoring strategy and recreational advisories. Ongoing research on benthic cyanobacteria is needed, particularly as their population increases in tandem with warming climate and reduced monsoonal floods.