Department or Program

Environmental Studies


Lake Auburn is the unfiltered drinking water source for the cities of Lewiston and Auburn, Maine. The lake is home to a variety of plankton, including the toxic species of cyanobacteria Gloeotrichia echinulata. The toxicity of this cyanobacteria comes from its production of the hepatotoxin microcystin. Exposure to microcystin in high concentrations can negatively impact the health of humans, animals, and other lake-dwelling species. Therefore, the annual occurrence of Gloeotrichia in Lake Auburn from May to September could pose a threat to public health. However, Gloeotrichia’s relationship with other plankton in Lake Auburn has never been analyzed before, and there is little information from any system telling about the relationship between these organisms. Throughout the 2016 sampling season (late May to early September) eight sites around the lake were sampled weekly for temperature, pH, dissolved oxygen, conductivity, chlorophyll (as an indicator of total phytoplankton), nutrients, and planktonic abundance (quantifying the Gloeotrichia density and classifying the zoo- and phytoplankton relative abundances). Zooplankton abundance increases as the season progresses, with copepods and cladocerans making up most of the zooplankton composition. Based on the relationships between plankton abundance and Gloeotrichia densities, there was no significantly supported or concrete evidence that other plankton occurrence influenced the growth or presence of G. echinulata. These findings suggest that G. echinulata growth and populations are not dependent on zoo- or phytoplankton presence, but rather suggests that other factors such as the cyanobacterium’s life cycle, weather patterns, lake morphology, lake temperature, nutrient levels, and light availability must drive these relationships. More consistent data relating to the system for longer periods of time would give a better trend for analysis.

Level of Access

Restricted: Campus/Bates Community Only Access

First Advisor

Holly Ewing

Date of Graduation


Degree Name

Bachelor of Science

Number of Pages


Components of Thesis

1 pdf file


Available to Bates community via local IP address or Bates login.