Date of Award

Summer 2019

Project Type


Program or Major

Biological Sciences

Degree Name

Doctor of Philosophy

First Advisor

James F Haney

Second Advisor

Alan Baker

Third Advisor

Larry Harris


Cyanobacteria are naturally occurring photosynthetic bacteria, ubiquitous in nature. Increases in temperature and nutrients have supported the proliferation of cyanobacterial growth globally, especially in freshwater systems. Many taxa can produce biotoxins referred to as “cyanotoxins”. While toxic cyanobacteria are a growing public health concern, little is known about the accumulation of cyanotoxins in lake food webs. This research investigates the seasonal occurrence and the potential role of toxic cyanobacteria in two lakes of contrasting water qualities and food web structures. Objectives of this study were to test the bioaccumulation of microcystins (MCs) and beta-methyl-alanine-amino acid (BMAA) in zooplankton. I further assessed the major zooplankton and phytoplankton communities using stable isotopes of carbon and nitrogen, with focus on the importance of zooplankton consumer types and diet sizes; picoplankton, nanoplankton and net plankton. The bioaccumulation of cyanotoxins in zooplankton were dependent on the trophic levels and feeding behaviors of the zooplankton, which vary by species, seasons and lakes. Cyanotoxin transfer was also dependent on the presence and composition of toxic cyanobacteria, including picocyanobacteria. Understanding the transfer of cyanotoxins to the zooplankton community have significant implications in determining the pathways and the bioaccumulation of cyanotoxins to higher trophic levels such as fish, wildlife and humans.