Shifts in cyanobacteria bloom phenology and phytoplankton community structure in response to two phosphorus immobilization strategies in Lake Carmi, VT
Manning, Audrey
Manning, Audrey
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Abstract
Lake Carmi is a shallow eutrophic lake in Franklin County, Vermont, that has experienced persistent cyanobacteria blooms over the past decades. Despite reductions in watershed nutrient export, legacy phosphorus (P) in the sediment coupled with a disproportionate contribution of nutrients from agricultural watershed land use, have slowed mitigation of eutrophication in Lake Carmi. Previous management efforts aimed to immobilize sediment P via aeration, however, due to aerator malfunction and destabilization of the water column, cyanobacteria bloom phenology shifted and biomass increased over the management period. Specifically, fall diatom blooms were displaced and replaced with coccoid cyanobacteria (Microcystis spp.). An aluminum sulfate (�alum�) treatment was applied in fall 2025 aimed at immobilizing sediment P and decreasing cyanobacteria biomass. This approach has been previously employed successfully is several Vermont lakes, including Lake Morey and Ticklenaked Pond. Here we provide an initial assessment of fall cyanobacteria bloom composition and biomass prior to, during, and following both management strategies (aeration and alum). Ongoing work will assess phytoplankton community composition, functional diversity, and cyanobacteria bloom phenology post-alum treatment.
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Date
1/1/2026
Student Status
Senior (Graduating in 2026)
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Poster
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Wildlife and Fisheries Biology
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Rubenstein School of Environment and Natural Resources
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Life Science