Document Type
Thesis
Degree Name
Master of Science (MSc)
Department
Biology
Faculty/School
Faculty of Science
First Advisor
Derek Gray
Advisor Role
Primary Supervisor
Abstract
Frame Lake, located in Yellowknife, Northwest Territories, is one of the city's main attractions. Unfortunately, urbanization and eutrophication have led to a decline in water quality in the lake. Eutrophication has caused a buildup of organic matter in sediments on the bottom of the lake, which can cause a high oxygen demand when processed by aerobic bacteria. Dissolved oxygen levels are high during the summer, but ice shields the lake from gas exchange with the atmosphere, leading to winter anoxia. This oxygen depletion makes it impossible for sensitive aquatic life, such as fish, to survive in the lake over the winter. One possible solution to winter anoxia is to install a hypolimnetic aerator to exchange oxygen between the lake's deep layers and the atmosphere. Past studies show that aeration will improve dissolved oxygen levels, and it may help break down accumulated organic matter and reduce nutrient levels in the water column. As part of a remediation project funded by Rio-Tinto Diamond Mines, a hypolimnetic aerator will be installed on Frame Lake in early summer 2024. To evaluate the effects of the aerator installation on the lake, data on the natural variability in water quality and biota in Frame Lake and comparable lakes within the region is necessary.
The objectives for my thesis were to examine seasonal variability in water quality and zooplankton communities in Frame Lake and two reference lakes, and to examine the relationships between water quality and zooplankton communities in those lakes to assess if aeration might lead to chemical or biological improvements in Frame Lake. I collected monthly water quality and zooplankton samples from Frame Lake and two reference lakes between March 2022 – November 2024. My results showed seasonal fluctuations in pH, conductivity, and dissolved oxygen in my study lakes, and confirmed that Frame Lake experiences anoxia once the ice cover forms. In addition, nutrient and conductivity levels were higher in Frame Lake than in the two reference lakes. Zooplankton samples showed seasonal variation in richness, diversity, evenness, and abundance, with highs in the summer and lows under ice in the winter. In addition, the abundance of zooplankton in Frame Lake was significantly lower under ice in comparison with the two reference lakes. When examining correlations between zooplankton communities and water quality variables that may be influenced by aeration, I found that zooplankton abundance and richness increased with higher levels of dissolved oxygen and decreased with higher levels of total nitrogen. These findings suggest that the installation of a hypolimnetic aerator in Frame Lake is needed to improve oxygen levels in Frame Lake during the winter, and that it may improve conditions such that zooplankton abundance and richness increase. Ultimately, the chemical and biological improvements that may result from aeration could improve the suitability of Frame Lake for future fish reintroduction.
Recommended Citation
Andreola, Nicole, "Examining Seasonality of Zooplankton Communities and Water Quality in Yellowknife Area Lakes, Northwest Territories" (2024). Theses and Dissertations (Comprehensive). 2664.
https://scholars.wlu.ca/etd/2664
Convocation Year
2024
Convocation Season
Fall