Poster Details
DO INTRODUCED FISH AND NUTRIENTS AFFECT THE PREVALENCE OF CYANOBACTERIA BLOOMS IN MOUNTAIN LAKES?
Mountain lakes are important freshwater resources due in part to their perceived pristine state, yet their isolation does not preclude them from anthropogenic disturbances such as fish stocking. Fish introductions can increase algal biomass and the frequency of algal blooms through changes in: 1) bottom-up forcing as fish increase rates of phosphorous recycling; and 2) top-down forcing as fish reduce the abundance of large-bodied grazers. The resilience of mountain lakes, like those in the Cascade Range, to fish stocking or other perturbations remains uncertain, especially in the context of varying landscape and climate. Variation in nutrients across this region may be a significant factor in phytoplankton growth. We analyzed existing monitoring data on 30 historically fishless lakes in the Oregon Cascades across a gradient of ultra-oligotrophic to eutrophic systems, either with or without stocked trout. Preliminary analysis suggests cladoceran abundances increase with decreasing fish stocking densities. Cladoceran grazers reduce the abundance of diatoms and in a potential competitive release, cyanobacteria levels were positively correlated with cladoceran abundance, possibly due to altered ratios of N:P availability via recycling by zooplankton. These results will guide upcoming field surveys and mesocosm experiments.
Lara Jansen (Primary Presenter/Author), Oak Ridge Institute for Science and Education Fellow c/o U.S. Environmental Protection Agency, jansen.lara@epa.gov;
Lara Jansen is an aquatic community ecologist and an ORISE postdoctoral fellow working on predictive models of benthic macroinvertebrate communities across the conterminous US in relation to watershed factors. Lara completed her PhD in Environmental Science at Portland State University in 2023, studying the drivers and dynamics of harmful algal blooms in mountain lakes with Dr. Angela Strecker. She also obtained a MS in Natural Resource Sciences at Cal Poly Humboldt University with a thesis focused on the downstream impacts of dam flow regulation on benthic macroinvertebrate and algal communities. She received her BS in Ecology and Evolution from University of California, San Diego, where she assisted on research from shark pH regulation to mountain lake zooplankton adaptation. Lara has also worked on other aquatic ecology projects with the Archbold Biological Station, Bureau of Land Management and Sandia National Laboratories.
Angela Strecker (Co-Presenter/Co-Author), Portland State University, strecker@pdx.edu;