Department or Program

Environmental Studies

Abstract

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 cyanobacteria Gloeotrichia echinulata. Gloeotrichia, like many other cyanobacterial species, produce the hepatotoxin microcystin. Exposure to microcystin in high concentrations can negatively impact the health of humans, animals, and other lake-dwelling species. Hence, the annual occurrence of Gloeotrichia in Lake Auburn from May to October could pose a threat to public health. However, Gloeotrichia’s cell-bound microcystin, has not previously been measured in Lake Auburn, and there is little information from any system about the controls of microcystin production in Gloeotrichia. An enzyme-linked immunosorbent assay (ELISA) was used to determine Gloeotrichia’s microcystin cell quota in 24 samples collected from four Lake Auburn sites over a period of six weeks surrounding Gloeotrichia’s peak summer bloom in 2015. Two runs of the toxicity test (ELISA) on the same set of samples produced inconsistent results, especially at low microcystin concentrations. This prevented quantitative comparison of Gloeotrichia’s cell-bound microcystin to factors that might be related to its production—temperature, pH, dissolved oxygen, chlorophyll (as an indicator of total phytoplankton), and Gloeotrichia cell density. Despite variability in quantification of microcystin across ELISA runs, two samples contained consistently quantifiable concentrations of the toxin. Even at these maximum values, Gloeotrichia’s intracellular microcystin concentration was at least five orders of magnitude below the World Health Organization’s drinking water toxicity standard of 1μg microcystin L-1. However, Gloeotrichia is not the only toxin-producing species in Lake Auburn, so total toxin concentration in the lake could still pose a threat to the quality of Lake Auburn as drinking water. For this reason, measurements of toxicity in Lake Auburn, and in other drinking water sources that contain toxin-producing cyanobacteria will likely soon be required by the United States Environmental Protection Agency. Variability in ELISA results, however, suggest that this method requires optimization for samples with low toxin concentrations, and comparisons of low levels of toxicity among samples analyzed in separate ELISA runs are not advised without further methodological refinement.

Level of Access

Restricted: Campus/Bates Community Only Access

First Advisor

Holly Ewing

Date of Graduation

5-2016

Degree Name

Bachelor of Arts

Number of Pages

88

Components of Thesis

1 pdf file

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