Summer 2013

Document Type

Master's Thesis (Open Access)

Degree Name

Master of Science (M.S.)


Science & Environmental Policy


Cyanobacterial harmful algal blooms (CHABs) dominate and disrupt aquatic ecosystems by virtue of their rapidly expanding biomass and the production of secondary metabolites, including potent toxins. Since 2007, toxin-producing CHABs have been documented in freshwater bodies draining into the Monterey Bay National Marine Sanctuary (MBNMS) located on the California Central Coast. In this study, we combined freshwater ecology and molecular biology approaches to characterize the abundance of potentially toxic cyanobacteria, intracellular microcystin levels, and presence of microcystin synthesis genes in association with environmental factors in Pinto Lake, located in Watsonville, CA, a freshwater body seasonally draining into the MBNMS. We observed potentially toxic cyanobacteria increasing with water temperature, thermocline depth and decreasing ammonium and nitrate with microcystin levels increasing with cyanobacteria abundance during the summer and autumn months of 2009 through 2011. Additionally, our results support an association between toxic Microcystis sp. abundance and abundance of Aphanizomenon sp. indicating a positive association between the presence of microcystin toxin genes, intracellular microcystin levels, and abundance of potentially toxic cyanobacteria in Pinto Lake.