Date of Completion


Document Type

Honors College Thesis


Environmental Sciences

Thesis Type

Honors College, College of Arts and Science Honors

First Advisor

Mindy Morales

Second Advisor

Andrew Schroth


Lake Champlain, Cyanobacteria, Cyanotoxins, Nutrient Limitation, Phytoplankton


Lake Champlain, located between the Adirondack Mountains of New York and the Green Mountains of Vermont, has had increased algal and cyanobacteria blooms during the summer months in recent years. In part due to climate change and increased nutrient loading into the lake due to anthropogenic activities, cyanobacteria blooms are of special concern, as cyanobacteria can produce cyanotoxins that are harmful to animal and human health. This research aims to assess the extent of synchrony between resource and primary producer nutrient stoichiometry (carbon: nitrogen: phosphorus; C:N:P) to determine trends relating to bloom initiation, growth, and senescence. We collected samples once per week in two eutrophic bays of Lake Champlain (Missisquoi Bay and Saint Albans Bay) from June-November 2021, and determined dissolved C:N:P in the water column and particulate C:N:P in seston. We found that seston stoichiometry diverged from the predicted optimal Redfield ratio (106:16:1, C:N:P) and from ambient resource stoichiometry the most during bloom events. Specifically, during a late August bloom in Missisquoi Bay, C:N decreased and C:P increased relative to ambient concentrations. In St. Albans Bay, C:N also decreased during the bloom period in August, but C:P remained stable relative to ambient nutrient stoichiometry. This was also reflected in nutrient concentrations, where seston N increased and ambient N remained stable. These trends suggest phytoplankton are experiencing fluctuating nutrient limitation with bloom development, where P limitation may initially trigger blooms, but N-limitation is induced during growth which may be compensated by nitrogen fixation. These results have important implications for bloom toxicity, as increased seston N may facilitate the production of N-rich neurotoxins such as anatoxin-a, produced by N-fixing genera.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.