Date of Graduation

Spring 5-2014

Degree Name

Bachelor of Science

Department or Program

Environmental Studies

Number of Pages

114

First Advisor

Holly Ewing

Abstract

Gloeotrichia echinulata, a toxic species of cyanobacteria, is present in at least 22 Maine lakes. This study examines G. echinulata abundances at 15 sites across three Maine lakes: Panther Pond in Raymond, Pleasant Lake in Casco, and Lake Auburn in Auburn, during summers 2011-13. In 2013, Lake Auburn - consistently the lake with the coolest temperatures and highest chlorophyll a levels - experienced a G. echinulata bloom (median 9 colonies/L) from early July-August, three weeks prior to the major bloom in Panther Pond (median 50 colonies/L). Meanwhile, Pleasant Lake experienced its highest G. echinulata levels (0.2 colonies/L) in early September. There was no evidence that within-lake variation in populations at Panther Pond or Pleasant Lake was a result of wind patterns. At Lake Auburn, the sites with the highest G. echinulata abundances were in the southeastern end. These southeast sites experienced the highest abundances when sampled within 72 hours of a north-northwest wind ≥ 9 km/h. An inlake mesocosm experiment in Panther Pond revealed that population growth rates depended on both G. echinulata density and the time of year but not the addition of phosphorus. These findings suggest no one major driver or indicator of G. echinulata populations but rather a dependence on many factors including the cyanobacterium’s life cycle, weather patterns, lake temperature, nutrient levels, and light availability.

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