Master of Science (MSc)
Faculty of Science
Lake water quality and the macroinvertebrate communities in Arctic regions are threatened by increased development and climate change. In order to understand how macroinvertebrate communities may respond to their changing environment, I performed a biological and water quality survey of 46 Arctic lakes located in the Gwich’in Settlement Area and the Inuvialuit Settlement Region of the Northwest Territories. Using these survey data, I performed two interrelated studies that asked: 1) how artificial pit lakes associated with gravel extraction for road development compared with natural lakes in terms of their water quality, morphometry, and macroinvertebrate communities; and 2) how water quality changes associated with permafrost thaw might affect macroinvertebrate communities. For both studies, lake morphometry, water quality, and biological data (macroinvertebrates, and fish presence) were collected. In the first study, gravel pit lakes were four times deeper, two times clearer, and five times smaller in their surface area than natural lakes. Additionally, important nutrients, including phosphorus and nitrogen were significantly lower in gravel pit lakes. Although gravel pit lakes differed in morphometry and nutrients, littoral macroinvertebrate communities did not differ significantly between the two lake types. Therefore, I concluded that despite their recent formation and unnatural morphometry, gravel pit lakes can support invertebrate communities typical of natural lakes in the region. For my second study, I developed multiple regression models to explain variation in macroinvertebrate richness, diversity, abundance, and percent sensitive species among lakes (R2 = 0.44-0.63). The most parsimonious models included variables affected by permafrost thaw, including chlorophyll-a, total nitrogen, total phosphorus, pH, conductivity, dissolved organic carbon, turbidity, and Secchi depth. Using these regression models, I showed that for every 5% change in variables associated with permafrost thaw, macroinvertebrate richness and diversity were predicted to increase at a rate of ~ 0.75% and ~2.5%, while total abundance and percent sensitive species were predicted to decrease by ~5% and ~10%, respectively. These results indicate that while richness and diversity may change little in response to water quality changes associated with permafrost thaw, the structure of communities may shift profoundly due to decreases in abundance and the loss of sensitive species. Taken together, my results suggest that while macroinvertebrate communities may benefit from some aspects of development (the creation of pit lakes), other environmental changes related to permafrost thaw are likely to negatively impact these important members of the lower food web.
Cohen, Rachel, "Environmental factors associated with benthic macroinvertebrate communities in Arctic lakes, Northwest Territories" (2019). Theses and Dissertations (Comprehensive). 2232.